Merged with trunk R846

Removed some overly verbose debug printing


git-svn-id: svn://localhost/ardour2/branches/midi@847 d708f5d6-7413-0410-9779-e7cbd77b26cf

86 files changed, 1398 insertions, 983 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000000..1a39c6d179
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,17 @@
+all: scons cscope
+
+scons:
+	scons
+
+sconsi:
+	scons --implicit-deps-unchanged
+
+cscope: cscope.out
+
+cscope.out: cscope.files
+	cscope -b
+
+cscope.files:
+	find . -name '*.[ch]' -o -name '*.cc' > $@
+
+.PHONY: all cscope.files sconsi cscope
diff --git a/SConstruct b/SConstruct
index e7e43a1405..b6a2ed64c5 100644
--- a/SConstruct
+++ b/SConstruct
@@ -457,6 +457,16 @@ libraries['flac'] = conf.Finish ()
 # or if that fails...
 #libraries['flac']    = LibraryInfo (LIBS='FLAC')
 
+# boost (we don't link against boost, just use some header files)
+
+libraries['boost'] = LibraryInfo ()
+conf = Configure (libraries['boost'])
+if conf.CheckHeader ('boost/shared_ptr.hpp', language='CXX') == 0:
+        print "Boost header files do not appear to be installed."
+        sys.exit (1)
+    
+libraries['boost'] = conf.Finish ()
+
 #
 # Check for liblo
 
diff --git a/gtk2_ardour/ardbg b/gtk2_ardour/ardbg
index 9d3f5bf6c7..115db85f59 100755
--- a/gtk2_ardour/ardbg
+++ b/gtk2_ardour/ardbg
@@ -1,3 +1,4 @@
 #!/bin/sh
-source ardev_common.sh
-exec gdb ./ardour.bin "$*"
+dir=`dirname "$0"`
+source $dir/ardev_common.sh
+exec gdb gtk2_ardour/ardour.bin $*
diff --git a/gtk2_ardour/ardev b/gtk2_ardour/ardev
index 017a7e337d..751557d634 100755
--- a/gtk2_ardour/ardev
+++ b/gtk2_ardour/ardev
@@ -1,4 +1,3 @@
 #!/bin/sh
-
-source ardev_common.sh
-exec ./ardour.bin --novst $*
+source `dirname "$0"`/ardev_common.sh
+exec gtk2_ardour/ardour.bin --novst "$*"
diff --git a/gtk2_ardour/ardev_common.sh b/gtk2_ardour/ardev_common.sh
index bf644f3e84..df4bb025c0 100755
--- a/gtk2_ardour/ardev_common.sh
+++ b/gtk2_ardour/ardev_common.sh
@@ -1,8 +1,10 @@
+cd `dirname "$0"`/..
+
 #export G_DEBUG=fatal_criticals
 
-export ARDOUR_PATH=./glade:./pixmaps:.
+export ARDOUR_PATH=gtk2_ardour/glade:gtk2_ardour/pixmaps:gtk2_ardour
 
-export LD_LIBRARY_PATH=../libs/surfaces/control_protocol:../libs/ardour:../libs/midi++2:../libs/pbd:../libs/soundtouch:../libs/gtkmm2ext:../libs/sigc++2:../libs/glibmm2:../libs/gtkmm2/atk:../libs/gtkmm2/pango:../libs/gtkmm2/gdk:../libs/gtkmm2/gtk:../libs/libgnomecanvasmm:../libs/libsndfile:../libs/appleutility:$LD_LIBRARY_PATH
+export LD_LIBRARY_PATH=libs/surfaces/control_protocol:libs/ardour:libs/midi++2:libs/pbd:libs/soundtouch:libs/gtkmm2ext:libs/sigc++2:libs/glibmm2:libs/gtkmm2/atk:libs/gtkmm2/pango:libs/gtkmm2/gdk:libs/gtkmm2/gtk:libs/libgnomecanvasmm:libs/libsndfile:libs/appleutility:$LD_LIBRARY_PATH
 
 # DYLD_LIBRARY_PATH is for darwin.
 export DYLD_LIBRARY_PATH=$LD_LIBRARY_PATH
diff --git a/gtk2_ardour/ardour_ui.cc b/gtk2_ardour/ardour_ui.cc
index 34718dfb1c..de117a1399 100644
--- a/gtk2_ardour/ardour_ui.cc
+++ b/gtk2_ardour/ardour_ui.cc
@@ -546,7 +546,7 @@ void
 ARDOUR_UI::count_recenabled_diskstreams (Route& route)
 {
 	Track* track = dynamic_cast<Track*>(&route);
-	if (track && track->diskstream().record_enabled()) {
+	if (track && track->diskstream()->record_enabled()) {
 		rec_enabled_diskstreams++;
 	}
 }
@@ -869,9 +869,9 @@ ARDOUR_UI::open_session ()
 
 
 void
-ARDOUR_UI::session_add_midi_route (bool disk)
+ARDOUR_UI::session_add_midi_route (bool disk, uint32_t how_many)
 {
-	boost::shared_ptr<Route> route;
+	list<boost::shared_ptr<MidiTrack> > tracks;
 
 	if (session == 0) {
 		warning << _("You cannot add a track without a session already loaded.") << endmsg;
@@ -880,14 +880,21 @@ ARDOUR_UI::session_add_midi_route (bool disk)
 
 	try { 
 		if (disk) {
-			if ((route = session->new_midi_track (/*mode*/)) == 0) {
-				error << _("could not create new midi track") << endmsg;
+
+			tracks = session->new_midi_track (ARDOUR::Normal, how_many);
+
+			if (tracks.size() != how_many) {
+				if (how_many == 1) {
+					error << _("could not create a new midi track") << endmsg;
+				} else {
+					error << string_compose (_("could not create %1 new midi tracks"), how_many) << endmsg;
+				}
 			}
-		} else {
+		} /*else {
 			if ((route = session->new_midi_route ()) == 0) {
 				error << _("could not create new midi bus") << endmsg;
 			}
-		}
+		}*/
 	}
 
 	catch (...) {
@@ -902,23 +909,38 @@ restart JACK with more ports."));
 
 
 void
-ARDOUR_UI::session_add_audio_route (bool disk, int32_t input_channels, int32_t output_channels, ARDOUR::TrackMode mode)
+ARDOUR_UI::session_add_audio_route (bool track, int32_t input_channels, int32_t output_channels, ARDOUR::TrackMode mode, uint32_t how_many)
 {
-	boost::shared_ptr<Route> route;
+	list<boost::shared_ptr<AudioTrack> > tracks;
+	Session::RouteList routes;
 
 	if (session == 0) {
-		warning << _("You cannot add a track without a session already loaded.") << endmsg;
+		warning << _("You cannot add a track or bus without a session already loaded.") << endmsg;
 		return;
 	}
 
 	try { 
-		if (disk) {
-			if ((route = session->new_audio_track (input_channels, output_channels, mode)) == 0) {
-				error << _("could not create new audio track") << endmsg;
+		if (track) {
+			tracks = session->new_audio_track (input_channels, output_channels, mode, how_many);
+
+			if (tracks.size() != how_many) {
+				if (how_many == 1) {
+					error << _("could not create a new audio track") << endmsg;
+				} else {
+					error << string_compose (_("could not create %1 new audio tracks"), how_many) << endmsg;
+				}
 			}
+
 		} else {
-			if ((route = session->new_audio_route (input_channels, output_channels)) == 0) {
-				error << _("could not create new audio bus") << endmsg;
+
+			routes = session->new_audio_route (input_channels, output_channels, how_many);
+
+			if (routes.size() != how_many) {
+				if (how_many == 1) {
+					error << _("could not create a new audio track") << endmsg;
+				} else {
+					error << string_compose (_("could not create %1 new audio tracks"), how_many) << endmsg;
+				}
 			}
 		}
 		
@@ -946,11 +968,6 @@ restart JACK with more ports."));
 }
 
 void
-ARDOUR_UI::diskstream_added (Diskstream* ds)
-{
-}
-
-void
 ARDOUR_UI::do_transport_locate (jack_nframes_t new_position)
 {
 	jack_nframes_t _preroll;
@@ -1200,7 +1217,7 @@ ARDOUR_UI::toggle_record_enable (uint32_t dstream)
 		Track* t;
 
 		if ((t = dynamic_cast<Track*>(r.get())) != 0) {
-			t->diskstream().set_record_enabled (!t->diskstream().record_enabled());
+			t->diskstream()->set_record_enabled (!t->diskstream()->record_enabled());
 		}
 	}
 	if (session == 0) {
@@ -1326,7 +1343,6 @@ ARDOUR_UI::start_engine ()
 			   settings for a new session 
 			*/
 			session->save_state ("");
-                        session->save_history ("");
 		}
 
 		/* there is too much going on, in too many threads, for us to 
@@ -1500,7 +1516,6 @@ ARDOUR_UI::save_state_canfail (string name)
 		}
 
 		if ((ret = session->save_state (name)) != 0) {
-                        session->save_history (name);
 			return ret;
 		}
 	}
@@ -2080,15 +2095,15 @@ ARDOUR_UI::add_route ()
 	}
 
 	ResponseType r = (ResponseType) add_route_dialog->run ();
-	
+
 	add_route_dialog->hide();
 
 	switch (r) {
-	case RESPONSE_ACCEPT:
-		break;
-	default:
-		return;
-		break;
+		case RESPONSE_ACCEPT:
+			break;
+		default:
+			return;
+			break;
 	}
 
 	if ((count = add_route_dialog->count()) <= 0) {
@@ -2110,25 +2125,20 @@ ARDOUR_UI::add_route ()
 
 	/* XXX do something with name template */
 
-	while (count) {
-		if (add_route_dialog->type() == ARDOUR::DataType::MIDI) {
-			if (track) {
-				session_add_midi_track();
-			} else  {
-				MessageDialog msg (*editor,
-				   _("Sorry, MIDI Busses are not supported at this time."));
-				msg.run ();
-				//session_add_midi_bus();
-			}
-		} else if (track) {
-			session_add_audio_track (input_chan, output_chan, add_route_dialog->mode());
-		} else {
-			session_add_audio_bus (input_chan, output_chan);
+	if (add_route_dialog->type() == ARDOUR::DataType::MIDI) {
+		if (track) {
+			session_add_midi_track(count);
+		} else  {
+			MessageDialog msg (*editor,
+					_("Sorry, MIDI Busses are not supported at this time."));
+			msg.run ();
+			//session_add_midi_bus();
 		}
-		--count;
-		
-		while (Main::events_pending()) {
-			Main::iteration ();
+	} else { 
+		if (track) {
+			session_add_audio_track (input_chan, output_chan, add_route_dialog->mode(), count);
+		} else {
+			session_add_audio_bus (input_chan, output_chan, count);
 		}
 	}
 }
diff --git a/gtk2_ardour/ardour_ui.h b/gtk2_ardour/ardour_ui.h
index 0af88eec18..1f5277b5fe 100644
--- a/gtk2_ardour/ardour_ui.h
+++ b/gtk2_ardour/ardour_ui.h
@@ -189,21 +189,21 @@ class ARDOUR_UI : public Gtkmm2ext::UI
 
 	void add_route ();
 	
-	void session_add_audio_track (int input_channels, int32_t output_channels, ARDOUR::TrackMode mode) {
-		session_add_audio_route (true, input_channels, output_channels, mode);
+	void session_add_audio_track (int input_channels, int32_t output_channels, ARDOUR::TrackMode mode, uint32_t how_many) {
+		session_add_audio_route (true, input_channels, output_channels, mode, how_many);
 	}
 
-	void session_add_audio_bus (int input_channels, int32_t output_channels) {
-		session_add_audio_route (false, input_channels, output_channels, ARDOUR::Normal);
+	void session_add_audio_bus (int input_channels, int32_t output_channels, uint32_t how_many) {
+		session_add_audio_route (false, input_channels, output_channels, ARDOUR::Normal, how_many);
 	}
 
-	void session_add_midi_track () {
-		session_add_midi_route (true);
+	void session_add_midi_track (uint32_t how_many) {
+		session_add_midi_route (true, how_many);
 	}
 
-	void session_add_midi_bus () {
+	/*void session_add_midi_bus () {
 		session_add_midi_route (false);
-	}
+	}*/
 
 	void set_engine (ARDOUR::AudioEngine&);
 
@@ -526,8 +526,6 @@ class ARDOUR_UI : public Gtkmm2ext::UI
 	sigc::connection point_one_second_connection;
 	sigc::connection point_zero_one_second_connection;
 
-	void diskstream_added (ARDOUR::Diskstream*);
-
 	gint session_menu (GdkEventButton *);
 
 	bool _will_create_new_session_automatically;
@@ -540,8 +538,8 @@ class ARDOUR_UI : public Gtkmm2ext::UI
 
 	void save_template ();
 
-	void session_add_audio_route (bool disk, int32_t input_channels, int32_t output_channels, ARDOUR::TrackMode mode);
-	void session_add_midi_route (bool disk);
+	void session_add_audio_route (bool disk, int32_t input_channels, int32_t output_channels, ARDOUR::TrackMode mode, uint32_t how_many);
+	void session_add_midi_route (bool disk, uint32_t how_many);
 
 	void set_transport_sensitivity (bool);
 
diff --git a/gtk2_ardour/ardour_ui_dialogs.cc b/gtk2_ardour/ardour_ui_dialogs.cc
index 5a1ec87462..c90480c1dd 100644
--- a/gtk2_ardour/ardour_ui_dialogs.cc
+++ b/gtk2_ardour/ardour_ui_dialogs.cc
@@ -76,10 +76,6 @@ ARDOUR_UI::connect_to_session (Session *s)
 	rec_button.set_sensitive (true);
 	shuttle_box.set_sensitive (true);
 	
-	if (session->n_diskstreams() == 0) {
-		session->DiskstreamAdded.connect (mem_fun(*this, &ARDOUR_UI::diskstream_added));
-	}
-
 	if (connection_editor) {
 		connection_editor->set_session (s);
 	}
@@ -156,7 +152,6 @@ ARDOUR_UI::unload_session ()
 			
 		case 1:
 			session->save_state ("");
-                        session->save_history ("");
 			break;
 		}
 	}
diff --git a/gtk2_ardour/ardour_ui_ed.cc b/gtk2_ardour/ardour_ui_ed.cc
index fc5ffb6e9c..2fe34127dc 100644
--- a/gtk2_ardour/ardour_ui_ed.cc
+++ b/gtk2_ardour/ardour_ui_ed.cc
@@ -194,14 +194,14 @@ ARDOUR_UI::install_actions ()
 	act = ActionManager::register_action (common_actions, X_("About"), _("About"),  mem_fun(*this, &ARDOUR_UI::show_splash));
 	act = ActionManager::register_toggle_action (common_actions, X_("ToggleColorManager"), _("Colors"), mem_fun(*this, &ARDOUR_UI::toggle_color_manager));
 	ActionManager::session_sensitive_actions.push_back (act);
-	act = ActionManager::register_action (common_actions, X_("AddAudioTrack"), _("Add Audio Track"), bind (mem_fun(*this, &ARDOUR_UI::session_add_audio_track), 1, 1, ARDOUR::Normal));
+	act = ActionManager::register_action (common_actions, X_("AddAudioTrack"), _("Add Audio Track"), bind (mem_fun(*this, &ARDOUR_UI::session_add_audio_track), 1, 1, ARDOUR::Normal, 1));
 	ActionManager::session_sensitive_actions.push_back (act);
-	act = ActionManager::register_action (common_actions, X_("AddAudioBus"), _("Add Audio Bus"), bind (mem_fun(*this, &ARDOUR_UI::session_add_audio_bus), 1, 1));
+	act = ActionManager::register_action (common_actions, X_("AddAudioBus"), _("Add Audio Bus"), bind (mem_fun(*this, &ARDOUR_UI::session_add_audio_bus), 1, 1, 1));
 	ActionManager::session_sensitive_actions.push_back (act);
-	act = ActionManager::register_action (common_actions, X_("AddMIDITrack"), _("Add MIDI Track"), (mem_fun(*this, &ARDOUR_UI::session_add_midi_track)));
-	ActionManager::session_sensitive_actions.push_back (act);
-	act = ActionManager::register_action (common_actions, X_("AddMidiBus"), _("Add Midi Bus"), mem_fun(*this, &ARDOUR_UI::session_add_midi_bus));
+	act = ActionManager::register_action (common_actions, X_("AddMIDITrack"), _("Add MIDI Track"), bind (mem_fun(*this, &ARDOUR_UI::session_add_midi_track), 1));
 	ActionManager::session_sensitive_actions.push_back (act);
+	//act = ActionManager::register_action (common_actions, X_("AddMidiBus"), _("Add Midi Bus"), mem_fun(*this, &ARDOUR_UI::session_add_midi_bus));
+	//ActionManager::session_sensitive_actions.push_back (act);
 	act = ActionManager::register_action (common_actions, X_("Save"), _("Save"),  bind (mem_fun(*this, &ARDOUR_UI::save_state), string("")));
 	ActionManager::session_sensitive_actions.push_back (act);
 	act = ActionManager::register_action (common_actions, X_("RemoveLastCapture"), _("Remove Last Capture"), mem_fun(*this, &ARDOUR_UI::remove_last_capture));
diff --git a/gtk2_ardour/audio_region_view.cc b/gtk2_ardour/audio_region_view.cc
index acde408c6b..93af5b3ec0 100644
--- a/gtk2_ardour/audio_region_view.cc
+++ b/gtk2_ardour/audio_region_view.cc
@@ -928,13 +928,13 @@ AudioRegionView::add_gain_point_event (ArdourCanvas::Item *item, GdkEvent *ev)
 		XMLNode &before = audio_region().get_state();
 		audio_region().set_envelope_active(true);
 		XMLNode &after = audio_region().get_state();
-		trackview.session().add_command (new MementoCommand<AudioRegion>(audio_region(), before, after));
+		trackview.session().add_command (new MementoCommand<AudioRegion>(audio_region(), &before, &after));
 	}
 
 	audio_region().envelope().add (fx, y);
 	
 	XMLNode &after = audio_region().envelope().get_state();
-	trackview.session().add_command (new MementoCommand<Curve>(audio_region().envelope(), before, after));
+	trackview.session().add_command (new MementoCommand<Curve>(audio_region().envelope(), &before, &after));
 	trackview.session().commit_reversible_command ();
 }
 
diff --git a/gtk2_ardour/audio_streamview.cc b/gtk2_ardour/audio_streamview.cc
index 523395c503..83d1825ef5 100644
--- a/gtk2_ardour/audio_streamview.cc
+++ b/gtk2_ardour/audio_streamview.cc
@@ -224,7 +224,7 @@ AudioStreamView::playlist_modified ()
 }
 
 void
-AudioStreamView::playlist_changed (Diskstream *ds)
+AudioStreamView::playlist_changed (boost::shared_ptr<Diskstream> ds)
 {
 	ENSURE_GUI_THREAD (bind (mem_fun (*this, &AudioStreamView::playlist_changed), ds));
 
@@ -398,7 +398,7 @@ AudioStreamView::setup_rec_box ()
 				rec_data_ready_connections.clear();
 					
 				// FIXME
-				AudioDiskstream* ads = dynamic_cast<AudioDiskstream*>(_trackview.get_diskstream());
+				boost::shared_ptr<AudioDiskstream> ads = boost::dynamic_pointer_cast<AudioDiskstream>(_trackview.get_diskstream());
 				assert(ads);
 
 				for (uint32_t n=0; n < ads->n_channels().get(DataType::AUDIO); ++n) {
@@ -430,8 +430,8 @@ AudioStreamView::setup_rec_box ()
 			AudioTrack* at;
 
 			at = _trackview.audio_track(); /* we know what it is already */
-			AudioDiskstream& ds = at->audio_diskstream();
-			jack_nframes_t frame_pos = ds.current_capture_start ();
+			boost::shared_ptr<AudioDiskstream> ds = at->audio_diskstream();
+			jack_nframes_t frame_pos = ds->current_capture_start ();
 			gdouble xstart = _trackview.editor.frame_to_pixel (frame_pos);
 			gdouble xend;
 			uint32_t fill_color;
diff --git a/gtk2_ardour/audio_streamview.h b/gtk2_ardour/audio_streamview.h
index 979240bd50..cf66637b9b 100644
--- a/gtk2_ardour/audio_streamview.h
+++ b/gtk2_ardour/audio_streamview.h
@@ -87,7 +87,7 @@ class AudioStreamView : public StreamView
 	void undisplay_diskstream ();
 	void redisplay_diskstream ();
 	void playlist_modified ();
-	void playlist_changed (ARDOUR::Diskstream *ds);
+	void playlist_changed (boost::shared_ptr<ARDOUR::Diskstream>);
 
 	void add_crossfade (ARDOUR::Crossfade*);
 	void remove_crossfade (ARDOUR::Crossfade*);
diff --git a/gtk2_ardour/automation_line.cc b/gtk2_ardour/automation_line.cc
index f3e30c4523..c0ba957af8 100644
--- a/gtk2_ardour/automation_line.cc
+++ b/gtk2_ardour/automation_line.cc
@@ -244,6 +244,9 @@ AutomationLine::AutomationLine (const string & name, TimeAxisView& tv, ArdourCan
 	line->signal_event().connect (mem_fun (*this, &AutomationLine::event_handler));
 
 	alist.StateChanged.connect (mem_fun(*this, &AutomationLine::list_changed));
+
+        trackview.session().register_with_memento_command_factory(_id, this);
+
 }
 
 AutomationLine::~AutomationLine ()
@@ -888,7 +891,7 @@ AutomationLine::start_drag (ControlPoint* cp, float fraction)
 	}
 
 	trackview.editor.current_session()->begin_reversible_command (str);
-	trackview.editor.current_session()->add_command (new MementoUndoCommand<AutomationLine>(*this, get_state()));
+	trackview.editor.current_session()->add_command (new MementoCommand<AutomationLine>(*this, &get_state(), 0));
 	
 	first_drag_fraction = fraction;
 	last_drag_fraction = fraction;
@@ -937,7 +940,7 @@ AutomationLine::end_drag (ControlPoint* cp)
 
 		update_pending = false;
 
-		trackview.editor.current_session()->add_command (new MementoRedoCommand<AutomationLine>(*this, get_state()));
+		trackview.editor.current_session()->add_command (new MementoCommand<AutomationLine>(*this, 0, &get_state()));
 		trackview.editor.current_session()->commit_reversible_command ();
 		trackview.editor.current_session()->set_dirty ();
 	}
@@ -1018,7 +1021,7 @@ AutomationLine::remove_point (ControlPoint& cp)
 
 	alist.erase (mr.start, mr.end);
 
-	trackview.editor.current_session()->add_command(new MementoCommand<AutomationLine>(*this, before, get_state()));
+	trackview.editor.current_session()->add_command(new MementoCommand<AutomationLine>(*this, &before, &get_state()));
 	trackview.editor.current_session()->commit_reversible_command ();
 	trackview.editor.current_session()->set_dirty ();
 }
@@ -1228,7 +1231,7 @@ AutomationLine::clear ()
 	/* parent must create command */
         XMLNode &before = get_state();
 	alist.clear();
-	trackview.editor.current_session()->add_command (new MementoCommand<AutomationLine>(*this, before, get_state()));
+	trackview.editor.current_session()->add_command (new MementoCommand<AutomationLine>(*this, &before, &get_state()));
 	trackview.editor.current_session()->commit_reversible_command ();
 	trackview.editor.current_session()->set_dirty ();
 }
diff --git a/gtk2_ardour/automation_time_axis.cc b/gtk2_ardour/automation_time_axis.cc
index 7025a11178..80ed2acd16 100644
--- a/gtk2_ardour/automation_time_axis.cc
+++ b/gtk2_ardour/automation_time_axis.cc
@@ -482,7 +482,7 @@ AutomationTimeAxisView::cut_copy_clear_one (AutomationLine& line, Selection& sel
 	case Cut:
 		if ((what_we_got = alist.cut (selection.time.front().start, selection.time.front().end)) != 0) {
 			editor.get_cut_buffer().add (what_we_got);
-			_session.add_command(new MementoCommand<AutomationList>(alist, before, alist.get_state()));
+			_session.add_command(new MementoCommand<AutomationList>(alist, &before, &alist.get_state()));
 			ret = true;
 		}
 		break;
@@ -494,7 +494,7 @@ AutomationTimeAxisView::cut_copy_clear_one (AutomationLine& line, Selection& sel
 
 	case Clear:
 		if ((what_we_got = alist.cut (selection.time.front().start, selection.time.front().end)) != 0) {
-			_session.add_command(new MementoCommand<AutomationList>(alist, before, alist.get_state()));
+			_session.add_command(new MementoCommand<AutomationList>(alist, &before, &alist.get_state()));
 			delete what_we_got;
 			what_we_got = 0;
 			ret = true;
@@ -526,7 +526,7 @@ AutomationTimeAxisView::reset_objects_one (AutomationLine& line, PointSelection&
 {
 	AutomationList& alist (line.the_list());
 
-	_session.add_command (new MementoUndoCommand<AutomationList>(alist, alist.get_state()));
+	_session.add_command (new MementoCommand<AutomationList>(alist, &alist.get_state(), 0));
 
 	for (PointSelection::iterator i = selection.begin(); i != selection.end(); ++i) {
 
@@ -569,7 +569,7 @@ AutomationTimeAxisView::cut_copy_clear_objects_one (AutomationLine& line, PointS
 		case Cut:
 			if ((what_we_got = alist.cut ((*i).start, (*i).end)) != 0) {
 				editor.get_cut_buffer().add (what_we_got);
-				_session.add_command (new MementoCommand<AutomationList>(alist, before, alist.get_state()));
+				_session.add_command (new MementoCommand<AutomationList>(alist, &before, &alist.get_state()));
 				ret = true;
 			}
 			break;
@@ -581,7 +581,7 @@ AutomationTimeAxisView::cut_copy_clear_objects_one (AutomationLine& line, PointS
 			
 		case Clear:
 			if ((what_we_got = alist.cut ((*i).start, (*i).end)) != 0) {
-				_session.add_command (new MementoCommand<AutomationList>(alist, before, alist.get_state()));
+				_session.add_command (new MementoCommand<AutomationList>(alist, &before, &alist.get_state()));
 				delete what_we_got;
 				what_we_got = 0;
 				ret = true;
@@ -640,7 +640,7 @@ AutomationTimeAxisView::paste_one (AutomationLine& line, jack_nframes_t pos, flo
 
         XMLNode &before = alist.get_state();
 	alist.paste (copy, pos, times);
-	_session.add_command (new MementoCommand<AutomationList>(alist, before, alist.get_state()));
+	_session.add_command (new MementoCommand<AutomationList>(alist, &before, &alist.get_state()));
 
 	return true;
 }
diff --git a/gtk2_ardour/axis_view.h b/gtk2_ardour/axis_view.h
index 12b7d32188..4ae8f8d46e 100644
--- a/gtk2_ardour/axis_view.h
+++ b/gtk2_ardour/axis_view.h
@@ -84,8 +84,6 @@ class AxisView : public virtual Selectable
 
 	Gtk::Label name_label;
 
-	bool _selected;
-
 	bool _marked_for_display;
 	
 }; /* class AxisView */
diff --git a/gtk2_ardour/editor.cc b/gtk2_ardour/editor.cc
index 5c3847730c..eceaf24d38 100644
--- a/gtk2_ardour/editor.cc
+++ b/gtk2_ardour/editor.cc
@@ -705,6 +705,7 @@ Editor::Editor (AudioEngine& eng)
 	ControlProtocol::ScrollTimeline.connect (mem_fun (*this, &Editor::control_scroll));
 	constructed = true;
 	instant_save ();
+
 }
 
 Editor::~Editor()
@@ -1339,6 +1340,9 @@ Editor::connect_to_session (Session *t)
 		no_route_list_redisplay = false;
 		redisplay_route_list ();
 	}
+
+        /* register for undo history */
+        session->register_with_memento_command_factory(_id, this);
 }
 
 void
@@ -1592,7 +1596,7 @@ Editor::build_track_region_context_menu (jack_nframes_t frame)
 	AudioTimeAxisView* atv = dynamic_cast<AudioTimeAxisView*> (clicked_axisview);
 
 	if (atv) {
-		Diskstream* ds;
+		boost::shared_ptr<Diskstream> ds;
 		Playlist* pl;
 		
 		if ((ds = atv->get_diskstream()) && ((pl = ds->playlist()))) {
@@ -1619,7 +1623,7 @@ Editor::build_track_crossfade_context_menu (jack_nframes_t frame)
 	AudioTimeAxisView* atv = dynamic_cast<AudioTimeAxisView*> (clicked_axisview);
 
 	if (atv) {
-		Diskstream* ds;
+		boost::shared_ptr<Diskstream> ds;
 		Playlist* pl;
 		AudioPlaylist* apl;
 
@@ -2888,7 +2892,7 @@ void
 Editor::commit_reversible_command ()
 {
 	if (session) {
-		session->commit_reversible_command (new MementoCommand<Editor>(*this, *before, get_state()));
+		session->commit_reversible_command (new MementoCommand<Editor>(*this, before, &get_state()));
 	}
 }
 
@@ -3016,7 +3020,7 @@ Editor::mapped_set_selected_regionview_from_click (RouteTimeAxisView& tv, uint32
 	Playlist* pl;
 	vector<Region*> results;
 	RegionView* marv;
-	Diskstream* ds;
+	boost::shared_ptr<Diskstream> ds;
 
 	if ((ds = tv.get_diskstream()) == 0) {
 		/* bus */
@@ -3242,7 +3246,7 @@ Editor::set_selected_regionview_from_region_list (Region& region, Selection::Ope
 			Playlist* pl;
 			vector<Region*> results;
 			RegionView* marv;
-			Diskstream* ds;
+			boost::shared_ptr<Diskstream> ds;
 			
 			if ((ds = tatv->get_diskstream()) == 0) {
 				/* bus */
@@ -3750,10 +3754,12 @@ Editor::get_valid_views (TimeAxisView* track, RouteGroup* group)
 void
 Editor::set_zoom_focus (ZoomFocus f)
 {
+	vector<string> txt = internationalize (zoom_focus_strings);
+	zoom_focus_selector.set_active_text (txt[(int)f]);
+	
 	if (zoom_focus != f) {
 		zoom_focus = f;
-		vector<string> txt = internationalize (zoom_focus_strings);
-		zoom_focus_selector.set_active_text (txt[(int)f]);
+
 		ZoomFocusChanged (); /* EMIT_SIGNAL */
 
 		instant_save ();
diff --git a/gtk2_ardour/editor.h b/gtk2_ardour/editor.h
index 40ece795b1..970acdc3a9 100644
--- a/gtk2_ardour/editor.h
+++ b/gtk2_ardour/editor.h
@@ -466,7 +466,7 @@ class Editor : public PublicEditor
 	void add_crossfade_context_items (AudioStreamView*, ARDOUR::Crossfade*, Gtk::Menu_Helpers::MenuList&, bool many);
 	void add_selection_context_items (Gtk::Menu_Helpers::MenuList&);
 
-	void handle_new_route (boost::shared_ptr<ARDOUR::Route>);
+	void handle_new_route (ARDOUR::Session::RouteList&);
 	void remove_route (TimeAxisView *);
 	bool route_removal;
 
diff --git a/gtk2_ardour/editor_audio_import.cc b/gtk2_ardour/editor_audio_import.cc
index de256ce0e6..2b704e7372 100644
--- a/gtk2_ardour/editor_audio_import.cc
+++ b/gtk2_ardour/editor_audio_import.cc
@@ -318,13 +318,13 @@ Editor::finish_bringing_in_audio (AudioRegion& region, uint32_t in_chans, uint32
 		
 	case ImportToTrack:
 		if (track) {
-			Playlist* playlist  = track->diskstream().playlist();
+			Playlist* playlist  = track->diskstream()->playlist();
 			
 			AudioRegion* copy = new AudioRegion (region);
 			begin_reversible_command (_("insert sndfile"));
                         XMLNode &before = playlist->get_state();
 			playlist->add_region (*copy, pos);
-			session->add_command (new MementoCommand<Playlist>(*playlist, before, playlist->get_state()));
+			session->add_command (new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
 			commit_reversible_command ();
 
 			pos += region.length();
@@ -333,17 +333,21 @@ Editor::finish_bringing_in_audio (AudioRegion& region, uint32_t in_chans, uint32
 		
 	case ImportAsTrack:
 	{ 
-		boost::shared_ptr<AudioTrack> at (session->new_audio_track (in_chans, out_chans, Normal));
-		copy = new AudioRegion (region);
-		at->diskstream().playlist()->add_region (*copy, pos);
+		list<boost::shared_ptr<AudioTrack> > at (session->new_audio_track (in_chans, out_chans, Normal, 1));
+		if (!at.empty()) {
+			copy = new AudioRegion (region);
+			at.front()->diskstream()->playlist()->add_region (*copy, pos);
+		}
 		break;
 	}
 
 	case ImportAsTapeTrack:
 	{
-		boost::shared_ptr<AudioTrack> at (session->new_audio_track (in_chans, out_chans, Destructive));
-		copy = new AudioRegion (region);
-		at->diskstream().playlist()->add_region (*copy, pos);
+		list<boost::shared_ptr<AudioTrack> > at (session->new_audio_track (in_chans, out_chans, Destructive));
+		if (!at.empty()) {
+			copy = new AudioRegion (region);
+			at.front()->diskstream()->playlist()->add_region (*copy, pos);
+		}
 		break;
 	}
 	}
diff --git a/gtk2_ardour/editor_keyboard.cc b/gtk2_ardour/editor_keyboard.cc
index f48d860d15..95289c7f5a 100644
--- a/gtk2_ardour/editor_keyboard.cc
+++ b/gtk2_ardour/editor_keyboard.cc
@@ -108,7 +108,7 @@ Editor::kbd_mute_unmute_region ()
 	    entered_regionview->region().set_muted (!entered_regionview->region().muted());
 		
 		XMLNode &after = entered_regionview->region().playlist()->get_state();
-		session->add_command (new MementoCommand<ARDOUR::Playlist>(*(entered_regionview->region().playlist()), before, after));
+		session->add_command (new MementoCommand<ARDOUR::Playlist>(*(entered_regionview->region().playlist()), &before, &after));
 		commit_reversible_command();
 	}
 }
diff --git a/gtk2_ardour/editor_markers.cc b/gtk2_ardour/editor_markers.cc
index ccc1415888..40f00c2e10 100644
--- a/gtk2_ardour/editor_markers.cc
+++ b/gtk2_ardour/editor_markers.cc
@@ -294,7 +294,7 @@ Editor::mouse_add_new_marker (jack_nframes_t where)
                 XMLNode &before = session->locations()->get_state();
 		session->locations()->add (location, true);
                 XMLNode &after = session->locations()->get_state();
-		session->add_command (new MementoCommand<Locations>(*(session->locations()), before, after));
+		session->add_command (new MementoCommand<Locations>(*(session->locations()), &before, &after));
 		session->commit_reversible_command ();
 	}
 }
@@ -334,7 +334,7 @@ Editor::really_remove_marker (Location* loc)
 	XMLNode &before = session->locations()->get_state();
 	session->locations()->remove (loc);
 	XMLNode &after = session->locations()->get_state();
-	session->add_command (new MementoCommand<Locations>(*(session->locations()), before, after));
+	session->add_command (new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	session->commit_reversible_command ();
 	return FALSE;
 }
@@ -847,7 +847,7 @@ Editor::marker_menu_rename ()
 	loc->set_name (txt);
 	
         XMLNode &after = session->locations()->get_state();
-	session->add_command (new MementoCommand<Locations>(*(session->locations()), before, after));
+	session->add_command (new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	commit_reversible_command ();
 }
 
@@ -876,14 +876,14 @@ Editor::new_transport_marker_menu_set_loop ()
 		session->locations()->add (loc, true);
 		session->set_auto_loop_location (loc);
                 XMLNode &after = session->locations()->get_state();
-		session->add_command (new MementoCommand<Locations>(*(session->locations()), before, after));
+		session->add_command (new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	}
 	else {
                 XMLNode &before = tll->get_state();
 		tll->set_hidden (false, this);
 		tll->set (temp_location->start(), temp_location->end());
                 XMLNode &after = tll->get_state();
-                session->add_command (new MementoCommand<Location>(*tll, before, after));
+                session->add_command (new MementoCommand<Location>(*tll, &before, &after));
 	}
 	
 	commit_reversible_command ();
@@ -904,13 +904,13 @@ Editor::new_transport_marker_menu_set_punch ()
 		session->locations()->add (tpl, true);
 		session->set_auto_punch_location (tpl);
                 XMLNode &after = session->locations()->get_state();
-		session->add_command (new MementoCommand<Locations>(*(session->locations()), before, after));
+		session->add_command (new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	} else {
                 XMLNode &before = tpl->get_state();
 		tpl->set_hidden(false, this);
 		tpl->set(temp_location->start(), temp_location->end());
                 XMLNode &after = tpl->get_state();
-                session->add_command (new MementoCommand<Location>(*tpl, before, after));
+                session->add_command (new MementoCommand<Location>(*tpl, &before, &after));
 	}
 	
 	commit_reversible_command ();
diff --git a/gtk2_ardour/editor_mouse.cc b/gtk2_ardour/editor_mouse.cc
index eb0bd432e3..df2c1d101c 100644
--- a/gtk2_ardour/editor_mouse.cc
+++ b/gtk2_ardour/editor_mouse.cc
@@ -1825,8 +1825,8 @@ Editor::fade_in_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent* even
 
         XMLNode &after = arv->audio_region().get_state();
         session->add_command(new MementoCommand<ARDOUR::AudioRegion>(arv->audio_region(),
-                                                                     before,
-                                                                     after));
+                                                                     &before,
+                                                                     &after));
 	commit_reversible_command ();
 	fade_in_drag_motion_callback (item, event);
 }
@@ -1921,7 +1921,7 @@ Editor::fade_out_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent* eve
 	arv->audio_region().set_fade_out_length (fade_length);
 
         XMLNode &after = arv->region().get_state();
-        session->add_command(new MementoCommand<ARDOUR::Region>(arv->region(), before, after));
+        session->add_command(new MementoCommand<ARDOUR::Region>(arv->region(), &before, &after));
 	commit_reversible_command ();
 
 	fade_out_drag_motion_callback (item, event);
@@ -2176,7 +2176,7 @@ Editor::marker_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent* event
 	}
 
 	XMLNode &after = session->locations()->get_state();
-	session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+	session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	commit_reversible_command ();
 	
 	marker_drag_line->hide();
@@ -2293,7 +2293,7 @@ Editor::meter_marker_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent*
                 XMLNode &before = map.get_state();
 		map.add_meter (marker->meter(), when);
 		XMLNode &after = map.get_state();
-                session->add_command(new MementoCommand<TempoMap>(map, before, after));
+                session->add_command(new MementoCommand<TempoMap>(map, &before, &after));
 		commit_reversible_command ();
 		
 		// delete the dummy marker we used for visual representation of copying.
@@ -2304,7 +2304,7 @@ Editor::meter_marker_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent*
 		XMLNode &before = map.get_state();
 		map.move_meter (marker->meter(), when);
 		XMLNode &after = map.get_state();
-                session->add_command(new MementoCommand<TempoMap>(map, before, after));
+                session->add_command(new MementoCommand<TempoMap>(map, &before, &after));
 		commit_reversible_command ();
 	}
 }
@@ -2425,7 +2425,7 @@ Editor::tempo_marker_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent*
 		XMLNode &before = map.get_state();
 		map.add_tempo (marker->tempo(), when);
 		XMLNode &after = map.get_state();
-		session->add_command (new MementoCommand<TempoMap>(map, before, after));
+		session->add_command (new MementoCommand<TempoMap>(map, &before, &after));
 		commit_reversible_command ();
 		
 		// delete the dummy marker we used for visual representation of copying.
@@ -2436,7 +2436,7 @@ Editor::tempo_marker_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent*
                 XMLNode &before = map.get_state();
 		map.move_tempo (marker->tempo(), when);
                 XMLNode &after = map.get_state();
-                session->add_command (new MementoCommand<TempoMap>(map, before, after));
+                session->add_command (new MementoCommand<TempoMap>(map, &before, &after));
 		commit_reversible_command ();
 	}
 }
@@ -2800,7 +2800,7 @@ Editor::region_drag_motion_callback (ArdourCanvas::Item* item, GdkEvent* event)
 			
 			insert_result = affected_playlists.insert (to_playlist);
 			if (insert_result.second) {
-				session->add_command (new MementoUndoCommand<Playlist>(*to_playlist, to_playlist->get_state()));
+				session->add_command (new MementoCommand<Playlist>(*to_playlist, &to_playlist->get_state(), 0));
 			}
 			
 			latest_regionview = 0;
@@ -3238,7 +3238,7 @@ Editor::region_drag_motion_callback (ArdourCanvas::Item* item, GdkEvent* event)
 					insert_result = motion_frozen_playlists.insert (pl);
 					if (insert_result.second) {
 						pl->freeze();
-						session->add_command(new MementoUndoCommand<Playlist>(*pl, pl->get_state()));
+						session->add_command(new MementoCommand<Playlist>(*pl, &pl->get_state(), 0));
 					}
 				}
 			}
@@ -3366,7 +3366,7 @@ Editor::region_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent* event
 			insert_result = motion_frozen_playlists.insert(to_playlist);
 			if (insert_result.second) {
 				to_playlist->freeze();
-                                session->add_command(new MementoUndoCommand<Playlist>(*to_playlist, to_playlist->get_state()));
+                                session->add_command(new MementoCommand<Playlist>(*to_playlist, &to_playlist->get_state(), 0));
 			}
 
 		}
@@ -3448,7 +3448,7 @@ Editor::region_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent* event
   out:
 	for (set<Playlist*>::iterator p = motion_frozen_playlists.begin(); p != motion_frozen_playlists.end(); ++p) {
 		(*p)->thaw ();
-		session->add_command (new MementoRedoCommand<Playlist>(*(*p), (*p)->get_state()));
+		session->add_command (new MementoCommand<Playlist>(*(*p), 0, & (*p)->get_state()));
 	}
 
 	motion_frozen_playlists.clear ();
@@ -3643,10 +3643,10 @@ Editor::start_selection_grab (ArdourCanvas::Item* item, GdkEvent* event)
 
 	Playlist* playlist = clicked_axisview->playlist();
 
-        before = &(playlist->get_state());
+        XMLNode *before = &(playlist->get_state());
 	clicked_axisview->playlist()->add_region (*region, selection->time[clicked_selection].start);
-        XMLNode &after = playlist->get_state();
-	session->add_command(new MementoCommand<Playlist>(*playlist, *before, after));
+        XMLNode *after = &(playlist->get_state());
+	session->add_command(new MementoCommand<Playlist>(*playlist, before, after));
 
 	commit_reversible_command ();
 	
@@ -4013,7 +4013,7 @@ Editor::trim_motion_callback (ArdourCanvas::Item* item, GdkEvent* event)
 			Playlist * pl = (*i)->region().playlist();
 			insert_result = motion_frozen_playlists.insert (pl);
 			if (insert_result.second) {
-                                session->add_command(new MementoUndoCommand<Playlist>(*pl, pl->get_state()));
+                                session->add_command(new MementoCommand<Playlist>(*pl, &pl->get_state(), 0));
 			}
 		}
 	}
@@ -4203,7 +4203,7 @@ Editor::trim_finished_callback (ArdourCanvas::Item* item, GdkEvent* event)
 		
 		for (set<Playlist*>::iterator p = motion_frozen_playlists.begin(); p != motion_frozen_playlists.end(); ++p) {
 			//(*p)->thaw ();
-                        session->add_command (new MementoRedoCommand<Playlist>(*(*p), (*p)->get_state()));
+                        session->add_command (new MementoCommand<Playlist>(*(*p), 0, &(*p)->get_state()));
                 }
 		
 		motion_frozen_playlists.clear ();
@@ -4241,7 +4241,7 @@ Editor::point_trim (GdkEvent* event)
                                         XMLNode &before = pl->get_state();
 					(*i)->region().trim_front (new_bound, this);	
                                         XMLNode &after = pl->get_state();
-                                        session->add_command(new MementoCommand<Playlist>(*pl, before, after));
+                                        session->add_command(new MementoCommand<Playlist>(*pl, &before, &after));
 				}
 			}
 
@@ -4252,7 +4252,7 @@ Editor::point_trim (GdkEvent* event)
 				XMLNode &before = pl->get_state();
 				rv->region().trim_front (new_bound, this);	
                                 XMLNode &after = pl->get_state();
-				session->add_command(new MementoCommand<Playlist>(*pl, before, after));
+				session->add_command(new MementoCommand<Playlist>(*pl, &before, &after));
 			}
 		}
 
@@ -4272,7 +4272,7 @@ Editor::point_trim (GdkEvent* event)
 					XMLNode &before = pl->get_state();
 					(*i)->region().trim_end (new_bound, this);
 					XMLNode &after = pl->get_state();
-					session->add_command(new MementoCommand<Playlist>(*pl, before, after));
+					session->add_command(new MementoCommand<Playlist>(*pl, &before, &after));
 				}
 			}
 
@@ -4283,7 +4283,7 @@ Editor::point_trim (GdkEvent* event)
 				XMLNode &before = pl->get_state();
 				rv->region().trim_end (new_bound, this);
                                 XMLNode &after = pl->get_state();
-				session->add_command (new MementoCommand<Playlist>(*pl, before, after));
+				session->add_command (new MementoCommand<Playlist>(*pl, &before, &after));
 			}
 		}
 
@@ -4306,7 +4306,7 @@ Editor::thaw_region_after_trim (RegionView& rv)
 
 	region.thaw (_("trimmed region"));
         XMLNode &after = region.playlist()->get_state();
-	session->add_command (new MementoRedoCommand<Playlist>(*(region.playlist()), after));
+	session->add_command (new MementoCommand<Playlist>(*(region.playlist()), 0, &after));
 
 	AudioRegionView* arv = dynamic_cast<AudioRegionView*>(&rv);
 	if (arv)
@@ -4451,7 +4451,7 @@ Editor::end_range_markerbar_op (ArdourCanvas::Item* item, GdkEvent* event)
 			newloc = new Location(temp_location->start(), temp_location->end(), "unnamed", Location::IsRangeMarker);
 			session->locations()->add (newloc, true);
                         XMLNode &after = session->locations()->get_state();
-			session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+			session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 			commit_reversible_command ();
 			
 			range_bar_drag_rect->hide();
@@ -4834,7 +4834,7 @@ Editor::mouse_brush_insert_region (RegionView* rv, jack_nframes_t pos)
         XMLNode &before = playlist->get_state();
 	playlist->add_region (*(new AudioRegion (arv->audio_region())), (jack_nframes_t) (pos * speed));
         XMLNode &after = playlist->get_state();
-	session->add_command(new MementoCommand<Playlist>(*playlist, before, after));
+	session->add_command(new MementoCommand<Playlist>(*playlist, &before, &after));
 	
 	// playlist is frozen, so we have to update manually
 	
diff --git a/gtk2_ardour/editor_ops.cc b/gtk2_ardour/editor_ops.cc
index 7115bfe634..2532222c0d 100644
--- a/gtk2_ardour/editor_ops.cc
+++ b/gtk2_ardour/editor_ops.cc
@@ -213,7 +213,7 @@ Editor::split_regions_at (jack_nframes_t where, RegionSelection& regions)
                         XMLNode &before = pl->get_state();
 			pl->split_region ((*a)->region(), where);
                         XMLNode &after = pl->get_state();
-                        session->add_command(new MementoCommand<Playlist>(*pl, before, after));
+                        session->add_command(new MementoCommand<Playlist>(*pl, &before, &after));
 		}
 
 		a = tmp;
@@ -236,7 +236,7 @@ Editor::remove_clicked_region ()
         XMLNode &before = playlist->get_state();
 	playlist->remove_region (&clicked_regionview->region());
         XMLNode &after = playlist->get_state();
-	session->add_command(new MementoCommand<Playlist>(*playlist, before, after));
+	session->add_command(new MementoCommand<Playlist>(*playlist, &before, &after));
 	commit_reversible_command ();
 }
 
@@ -412,7 +412,7 @@ Editor::nudge_forward (bool next)
                         XMLNode &before = r.playlist()->get_state();
 			r.set_position (r.position() + distance, this);
                         XMLNode &after = r.playlist()->get_state();
-			session->add_command (new MementoCommand<Playlist>(*(r.playlist()), before, after));
+			session->add_command (new MementoCommand<Playlist>(*(r.playlist()), &before, &after));
 		}
 
 		commit_reversible_command ();
@@ -452,7 +452,7 @@ Editor::nudge_backward (bool next)
 				r.set_position (0, this);
 			}
                         XMLNode &after = r.playlist()->get_state();
-			session->add_command(new MementoCommand<Playlist>(*(r.playlist()), before, after));
+			session->add_command(new MementoCommand<Playlist>(*(r.playlist()), &before, &after));
 		}
 
 		commit_reversible_command ();
@@ -488,7 +488,7 @@ Editor::nudge_forward_capture_offset ()
 			XMLNode &before = r.playlist()->get_state();
 			r.set_position (r.position() + distance, this);
 			XMLNode &after = r.playlist()->get_state();
-			session->add_command(new MementoCommand<Playlist>(*(r.playlist()), before, after));
+			session->add_command(new MementoCommand<Playlist>(*(r.playlist()), &before, &after));
 		}
 
 		commit_reversible_command ();
@@ -520,7 +520,7 @@ Editor::nudge_backward_capture_offset ()
 				r.set_position (0, this);
 			}
                         XMLNode &after = r.playlist()->get_state();
-			session->add_command(new MementoCommand<Playlist>(*(r.playlist()), before, after));
+			session->add_command(new MementoCommand<Playlist>(*(r.playlist()), &before, &after));
 		}
 
 		commit_reversible_command ();
@@ -1300,7 +1300,7 @@ Editor::add_location_from_selection ()
         XMLNode &before = session->locations()->get_state();
 	session->locations()->add (location, true);
         XMLNode &after = session->locations()->get_state();
-	session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+	session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	session->commit_reversible_command ();
 }
 
@@ -1314,7 +1314,7 @@ Editor::add_location_from_playhead_cursor ()
         XMLNode &before = session->locations()->get_state();
 	session->locations()->add (location, true);
         XMLNode &after = session->locations()->get_state();
-	session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+	session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	session->commit_reversible_command ();
 }
 
@@ -1333,7 +1333,7 @@ Editor::add_location_from_audio_region ()
         XMLNode &before = session->locations()->get_state();
 	session->locations()->add (location, true);
         XMLNode &after = session->locations()->get_state();
-	session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+	session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	session->commit_reversible_command ();
 }
 
@@ -1752,7 +1752,7 @@ Editor::clear_markers ()
                 XMLNode &before = session->locations()->get_state();
 		session->locations()->clear_markers ();
                 XMLNode &after = session->locations()->get_state();
-		session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+		session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 		session->commit_reversible_command ();
 	}
 }
@@ -1773,7 +1773,7 @@ Editor::clear_ranges ()
 		if (punchloc) session->locations()->add (punchloc);
 		
                 XMLNode &after = session->locations()->get_state();
-		session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+		session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 		session->commit_reversible_command ();
 	}
 }
@@ -1785,7 +1785,7 @@ Editor::clear_locations ()
         XMLNode &before = session->locations()->get_state();
 	session->locations()->clear ();
         XMLNode &after = session->locations()->get_state();
-	session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+	session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	session->commit_reversible_command ();
 	session->locations()->clear ();
 }
@@ -1835,7 +1835,7 @@ Editor::insert_region_list_drag (AudioRegion& region, int x, int y)
 	begin_reversible_command (_("insert dragged region"));
         XMLNode &before = playlist->get_state();
 	playlist->add_region (*(new AudioRegion (region)), where, 1.0);
-	session->add_command(new MementoCommand<Playlist>(*playlist, before, playlist->get_state()));
+	session->add_command(new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
 	commit_reversible_command ();
 }
 
@@ -1871,7 +1871,7 @@ Editor::insert_region_list_selection (float times)
 	begin_reversible_command (_("insert region"));
         XMLNode &before = playlist->get_state();
 	playlist->add_region (*(createRegion (*region)), edit_cursor->current_frame, times);
-	session->add_command(new MementoCommand<Playlist>(*playlist, before, playlist->get_state()));
+	session->add_command(new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
 	commit_reversible_command ();
 }
 
@@ -2311,7 +2311,7 @@ Editor::separate_region_from_selection ()
 					}
 
 					if (doing_undo) 
-                                            session->add_command(new MementoCommand<Playlist>(*playlist, *before, playlist->get_state()));
+                                            session->add_command(new MementoCommand<Playlist>(*playlist, before, &playlist->get_state()));
 				}
 			}
 		}
@@ -2364,7 +2364,7 @@ Editor::separate_regions_using_location (Location& loc)
 
 					playlist->partition ((jack_nframes_t)(loc.start() * speed), (jack_nframes_t)(loc.end() * speed), true);
 					if (doing_undo) 
-                                            session->add_command(new MementoCommand<Playlist>(*playlist, *before, playlist->get_state()));
+                                            session->add_command(new MementoCommand<Playlist>(*playlist, before, &playlist->get_state()));
 				}
 			}
 		}
@@ -2435,7 +2435,7 @@ Editor::crop_region_to_selection ()
                         XMLNode &before = (*i)->get_state();
 			region->trim_to (start, cnt, this);
                         XMLNode &after = (*i)->get_state();
-			session->add_command (new MementoCommand<Playlist>(*(*i), before, after));
+			session->add_command (new MementoCommand<Playlist>(*(*i), &before, &after));
 		}
 
 		commit_reversible_command ();
@@ -2477,7 +2477,7 @@ Editor::region_fill_track ()
 
 		XMLNode &before = pl->get_state();
 		pl->add_region (*(new AudioRegion (*ar)), ar->last_frame(), times);
-		session->add_command (new MementoCommand<Playlist>(*pl, before, pl->get_state()));
+		session->add_command (new MementoCommand<Playlist>(*pl, &before, &pl->get_state()));
 	}
 
 	commit_reversible_command ();
@@ -2527,7 +2527,7 @@ Editor::region_fill_selection ()
 		
                 XMLNode &before = playlist->get_state();
 		playlist->add_region (*(createRegion (*region)), start, times);
-		session->add_command (new MementoCommand<Playlist>(*playlist, before, playlist->get_state()));
+		session->add_command (new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
 	}
 	
 	commit_reversible_command ();			
@@ -2545,7 +2545,7 @@ Editor::set_a_regions_sync_position (Region& region, jack_nframes_t position)
         XMLNode &before = region.playlist()->get_state();
 	region.set_sync_position (position);
         XMLNode &after = region.playlist()->get_state();
-	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), before, after));
+	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), &before, &after));
 	commit_reversible_command ();
 }
 
@@ -2566,7 +2566,7 @@ Editor::set_region_sync_from_edit_cursor ()
         XMLNode &before = region.playlist()->get_state();
 	region.set_sync_position (edit_cursor->current_frame);
         XMLNode &after = region.playlist()->get_state();
-	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), before, after));
+	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), &before, &after));
 	commit_reversible_command ();
 }
 
@@ -2579,7 +2579,7 @@ Editor::remove_region_sync ()
                 XMLNode &before = region.playlist()->get_state();
 		region.clear_sync_position ();
                 XMLNode &after = region.playlist()->get_state();
-		session->add_command(new MementoCommand<Playlist>(*(region.playlist()), before, after));
+		session->add_command(new MementoCommand<Playlist>(*(region.playlist()), &before, &after));
 		commit_reversible_command ();
 	}
 }
@@ -2595,7 +2595,7 @@ Editor::naturalize ()
                 XMLNode &before = (*i)->region().get_state();
 		(*i)->region().move_to_natural_position (this);
                 XMLNode &after = (*i)->region().get_state();
-		session->add_command (new MementoCommand<Region>((*i)->region(), before, after));
+		session->add_command (new MementoCommand<Region>((*i)->region(), &before, &after));
 	}
 	commit_reversible_command ();
 }
@@ -2670,7 +2670,7 @@ Editor::align_selection_relative (RegionPoint point, jack_nframes_t position)
 		}
 
                 XMLNode &after = region.playlist()->get_state();
-		session->add_command(new MementoCommand<Playlist>(*(region.playlist()), before, after));
+		session->add_command(new MementoCommand<Playlist>(*(region.playlist()), &before, &after));
 
 	}
 
@@ -2723,7 +2723,7 @@ Editor::align_region_internal (Region& region, RegionPoint point, jack_nframes_t
 	}
 
 	XMLNode &after = region.playlist()->get_state();
-	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), before, after));
+	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), &before, &after));
 }	
 
 void
@@ -2748,7 +2748,7 @@ Editor::trim_region_to_edit_cursor ()
         XMLNode &before = region.playlist()->get_state();
 	region.trim_end( session_frame_to_track_frame(edit_cursor->current_frame, speed), this);
         XMLNode &after = region.playlist()->get_state();
-	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), before, after));
+	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), &before, &after));
 	commit_reversible_command ();
 }
 
@@ -2774,7 +2774,7 @@ Editor::trim_region_from_edit_cursor ()
         XMLNode &before = region.playlist()->get_state();
 	region.trim_front ( session_frame_to_track_frame(edit_cursor->current_frame, speed), this);
         XMLNode &after = region.playlist()->get_state();
-	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), before, after));
+	session->add_command(new MementoCommand<Playlist>(*(region.playlist()), &before, &after));
 	commit_reversible_command ();
 }
 
@@ -2889,7 +2889,7 @@ Editor::bounce_range_selection ()
                 XMLNode &before = playlist->get_state();
 		atv->audio_track()->bounce_range (start, cnt, itt);
                 XMLNode &after = playlist->get_state();
-		session->add_command (new MementoCommand<Playlist> (*playlist, before, after));
+		session->add_command (new MementoCommand<Playlist> (*playlist, &before, &after));
 	}
 	
 	commit_reversible_command ();
@@ -3007,7 +3007,7 @@ Editor::cut_copy_regions (CutCopyOp op)
 				insert_result = freezelist.insert (pl);
 				if (insert_result.second) {
 					pl->freeze ();
-                                        session->add_command (new MementoUndoCommand<Playlist>(*pl, pl->get_state()));
+                                        session->add_command (new MementoCommand<Playlist>(*pl, &pl->get_state(), 0));
 				}
 			}
 		}
@@ -3071,7 +3071,7 @@ Editor::cut_copy_regions (CutCopyOp op)
 	
 	for (set<Playlist*>::iterator pl = freezelist.begin(); pl != freezelist.end(); ++pl) {
 		(*pl)->thaw ();
-		session->add_command (new MementoRedoCommand<Playlist>(*(*pl), (*pl)->get_state()));
+		session->add_command (new MementoCommand<Playlist>(*(*pl), 0, &(*pl)->get_state()));
 	}
 }
 
@@ -3186,7 +3186,7 @@ Editor::paste_named_selection (float times)
 
                 XMLNode &before = apl->get_state();
 		apl->paste (**chunk, edit_cursor->current_frame, times);
-		session->add_command(new MementoCommand<AudioPlaylist>(*apl, before, apl->get_state()));
+		session->add_command(new MementoCommand<AudioPlaylist>(*apl, &before, &apl->get_state()));
 
 		if (tmp != ns->playlists.end()) {
 			chunk = tmp;
@@ -3217,7 +3217,7 @@ Editor::duplicate_some_regions (RegionSelection& regions, float times)
  		playlist = (*i)->region().playlist();
                 XMLNode &before = playlist->get_state();
 		playlist->duplicate (r, r.last_frame(), times);
-		session->add_command(new MementoCommand<Playlist>(*playlist, before, playlist->get_state()));
+		session->add_command(new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
 
 		c.disconnect ();
 
@@ -3258,7 +3258,7 @@ Editor::duplicate_selection (float times)
                 XMLNode &before = playlist->get_state();
 		playlist->duplicate (**ri, selection->time[clicked_selection].end, times);
                 XMLNode &after = playlist->get_state();
-		session->add_command (new MementoCommand<Playlist>(*playlist, before, after));
+		session->add_command (new MementoCommand<Playlist>(*playlist, &before, &after));
 
 		++ri;
 		if (ri == new_regions.end()) {
@@ -3309,7 +3309,7 @@ Editor::clear_playlist (Playlist& playlist)
         XMLNode &before = playlist.get_state();
 	playlist.clear ();
         XMLNode &after = playlist.get_state();
-	session->add_command (new MementoCommand<Playlist>(playlist, before, after));
+	session->add_command (new MementoCommand<Playlist>(playlist, &before, &after));
 	commit_reversible_command ();
 }
 
@@ -3346,7 +3346,7 @@ Editor::nudge_track (bool use_edit_cursor, bool forwards)
                 XMLNode &before = playlist->get_state();
 		playlist->nudge_after (start, distance, forwards);
                 XMLNode &after = playlist->get_state();
-		session->add_command (new MementoCommand<Playlist>(*playlist, before, after));
+		session->add_command (new MementoCommand<Playlist>(*playlist, &before, &after));
 	}
 	
 	commit_reversible_command ();			
@@ -3402,7 +3402,7 @@ Editor::normalize_region ()
 			continue;
  		XMLNode &before = arv->region().get_state();
 		arv->audio_region().normalize_to (0.0f);
-		session->add_command (new MementoCommand<Region>(arv->region(), before, arv->region().get_state()));
+		session->add_command (new MementoCommand<Region>(arv->region(), &before, &arv->region().get_state()));
 	}
 
 	commit_reversible_command ();
@@ -3429,7 +3429,7 @@ Editor::denormalize_region ()
 			continue;
 		XMLNode &before = arv->region().get_state();
 		arv->audio_region().set_scale_amplitude (1.0f);
-		session->add_command (new MementoCommand<Region>(arv->region(), before, arv->region().get_state()));
+		session->add_command (new MementoCommand<Region>(arv->region(), &before, &arv->region().get_state()));
 	}
 
 	commit_reversible_command ();
@@ -3476,7 +3476,7 @@ Editor::apply_filter (AudioFilter& filter, string command)
                         XMLNode &before = playlist->get_state();
 			playlist->replace_region (arv->region(), *(filter.results.front()), arv->region().position());
                         XMLNode &after = playlist->get_state();
-			session->add_command(new MementoCommand<Playlist>(*playlist, before, after));
+			session->add_command(new MementoCommand<Playlist>(*playlist, &before, &after));
 		} else {
 			goto out;
 		}
diff --git a/gtk2_ardour/editor_route_list.cc b/gtk2_ardour/editor_route_list.cc
index bb38953038..512e2ecef1 100644
--- a/gtk2_ardour/editor_route_list.cc
+++ b/gtk2_ardour/editor_route_list.cc
@@ -30,6 +30,8 @@
 #include "mixer_strip.h"
 #include "gui_thread.h"
 
+#include <pbd/unknown_type.h>
+
 #include <ardour/route.h>
 
 #include "i18n.h"
@@ -41,79 +43,81 @@ using namespace Gtk;
 
 
 void
-Editor::handle_new_route (boost::shared_ptr<Route> route)
+Editor::handle_new_route (Session::RouteList& routes)
 {
-	ENSURE_GUI_THREAD(bind (mem_fun(*this, &Editor::handle_new_route), route));
-
+	ENSURE_GUI_THREAD(bind (mem_fun(*this, &Editor::handle_new_route), routes));
+	
 	TimeAxisView *tv;
+	RouteTimeAxisView *rtv;
 	TreeModel::Row parent;
 	TreeModel::Row row;
 
-	if (route->hidden()) {
-		return;
-	}
+	for (Session::RouteList::iterator x = routes.begin(); x != routes.end(); ++x) {
+		boost::shared_ptr<Route> route = (*x);
 
-	// FIXME
-	DataType type = route->default_type();
-	assert(type == ARDOUR::DataType::AUDIO || type == ARDOUR::DataType::MIDI);
-	
-	if (type == ARDOUR::DataType::AUDIO)
-		tv = new AudioTimeAxisView (*this, *session, route, track_canvas);
-	else
-		tv = new MidiTimeAxisView (*this, *session, route, track_canvas);
-	
+		if (route->hidden()) {
+			return;
+		}
+		
+		if (route->default_type() == ARDOUR::DataType::AUDIO)
+			tv = new AudioTimeAxisView (*this, *session, route, track_canvas);
+		else if (route->default_type() == ARDOUR::DataType::MIDI)
+			tv = new MidiTimeAxisView (*this, *session, route, track_canvas);
+		else
+			throw unknown_type();
+		
 #if 0
-	if (route_display_model->children().size() == 0) {
+		if (route_display_model->children().size() == 0) {
+			
+			/* set up basic entries */
+			
+			TreeModel::Row row;
+			
+			row = *(route_display_model->append());  // path = "0"
+			row[route_display_columns.text] = _("Busses");
+			row[route_display_columns.tv] = 0;
+			row = *(route_display_model->append());  // path = "1"
+			row[route_display_columns.text] = _("Tracks");
+			row[route_display_columns.tv] = 0;
+			
+		}
 		
-                /* set up basic entries */
-
-		TreeModel::Row row;
+		if (dynamic_cast<AudioTrack*>(route.get()) != 0) {
+			TreeModel::iterator iter = route_display_model->get_iter ("1");  // audio tracks 
+			parent = *iter;
+		} else {
+			TreeModel::iterator iter = route_display_model->get_iter ("0");  // busses
+			parent = *iter;
+		}
 		
-		row = *(route_display_model->append());  // path = "0"
-		row[route_display_columns.text] = _("Busses");
-		row[route_display_columns.tv] = 0;
-		row = *(route_display_model->append());  // path = "1"
-		row[route_display_columns.text] = _("Tracks");
-		row[route_display_columns.tv] = 0;
-
-	}
-
-	if (dynamic_cast<AudioTrack*>(route.get()) != 0) {
-		TreeModel::iterator iter = route_display_model->get_iter ("1");  // audio tracks 
-		parent = *iter;
-	} else {
-		TreeModel::iterator iter = route_display_model->get_iter ("0");  // busses
-		parent = *iter;
-	}
-	
-
-	row = *(route_display_model->append (parent.children()));
+		
+		row = *(route_display_model->append (parent.children()));
 #else 
-	row = *(route_display_model->append ());
+		row = *(route_display_model->append ());
 #endif
-
-	row[route_display_columns.text] = route->name();
-	row[route_display_columns.visible] = tv->marked_for_display();
-	row[route_display_columns.tv] = tv;
-	
-	track_views.push_back (tv);
-
-	ignore_route_list_reorder = true;
-	
-	RouteTimeAxisView* rtv = NULL;
-	if ((rtv = dynamic_cast<RouteTimeAxisView*> (tv)) != 0) {
-		/* added a new fresh one at the end */
-		if (rtv->route()->order_key(N_("editor")) == -1) {
-		        rtv->route()->set_order_key (N_("editor"), route_display_model->children().size()-1);
+		
+		row[route_display_columns.text] = route->name();
+		row[route_display_columns.visible] = tv->marked_for_display();
+		row[route_display_columns.tv] = tv;
+		
+		track_views.push_back (tv);
+		
+		ignore_route_list_reorder = true;
+		
+		if ((rtv = dynamic_cast<RouteTimeAxisView*> (tv)) != 0) {
+			/* added a new fresh one at the end */
+			if (rtv->route()->order_key(N_("editor")) == -1) {
+				rtv->route()->set_order_key (N_("editor"), route_display_model->children().size()-1);
+			}
 		}
+		
+		ignore_route_list_reorder = false;
+		
+		route->gui_changed.connect (mem_fun(*this, &Editor::handle_gui_changes));
+		
+		tv->GoingAway.connect (bind (mem_fun(*this, &Editor::remove_route), tv));
 	}
 
-	ignore_route_list_reorder = false;
-	
-	route->gui_changed.connect (mem_fun(*this, &Editor::handle_gui_changes));
-
-	tv->GoingAway.connect (bind (mem_fun(*this, &Editor::remove_route), tv));
-	
 	editor_mixer_button.set_sensitive(true);
 }
 
@@ -190,9 +194,9 @@ Editor::hide_track_in_display (TimeAxisView& tv)
 		}
 	}
 
-	AudioTimeAxisView* atv = dynamic_cast<AudioTimeAxisView*> (&tv);
+	RouteTimeAxisView* rtv = dynamic_cast<RouteTimeAxisView*> (&tv);
 
-	if (atv && current_mixer_strip && (atv->route() == current_mixer_strip->route())) {
+	if (rtv && current_mixer_strip && (rtv->route() == current_mixer_strip->route())) {
 		// this will hide the mixer strip
 		set_selected_mixer_strip (tv);
 	}
@@ -234,7 +238,7 @@ Editor::redisplay_route_list ()
 
 	for (n = 0, order = 0, position = 0, i = rows.begin(); i != rows.end(); ++i) {
 		TimeAxisView *tv = (*i)[route_display_columns.tv];
-		AudioTimeAxisView* at; 
+		RouteTimeAxisView* rt; 
 
 		if (tv == 0) {
 			// just a "title" row
@@ -247,8 +251,8 @@ Editor::redisplay_route_list ()
 			   to tracks.
 			*/
 			
-			if ((at = dynamic_cast<AudioTimeAxisView*> (tv)) != 0) {
-				at->route()->set_order_key (N_("editor"), order);
+			if ((rt = dynamic_cast<RouteTimeAxisView*> (tv)) != 0) {
+				rt->route()->set_order_key (N_("editor"), order);
 				++order;
 			}
 		}
@@ -500,9 +504,7 @@ Editor::initial_route_list_display ()
 
 	route_display_model->clear ();
 
-	for (Session::RouteList::iterator i = r.begin(); i != r.end(); ++i) {
-		handle_new_route (*i);
-	}
+	handle_new_route (r);
 
 	no_route_list_redisplay = false;
 
diff --git a/gtk2_ardour/editor_tempodisplay.cc b/gtk2_ardour/editor_tempodisplay.cc
index ff99c76351..e5b1a67cf3 100644
--- a/gtk2_ardour/editor_tempodisplay.cc
+++ b/gtk2_ardour/editor_tempodisplay.cc
@@ -278,7 +278,7 @@ Editor::mouse_add_new_tempo_event (jack_nframes_t frame)
         XMLNode &before = map.get_state();
 	map.add_tempo (Tempo (bpm), requested);
         XMLNode &after = map.get_state();
-	session->add_command(new MementoCommand<TempoMap>(map, before, after));
+	session->add_command(new MementoCommand<TempoMap>(map, &before, &after));
 	commit_reversible_command ();
 	
 	map.dump (cerr);
@@ -318,7 +318,7 @@ Editor::mouse_add_new_meter_event (jack_nframes_t frame)
 	begin_reversible_command (_("add meter mark"));
         XMLNode &before = map.get_state();
 	map.add_meter (Meter (bpb, note_type), requested);
-	session->add_command(new MementoCommand<TempoMap>(map, before, map.get_state()));
+	session->add_command(new MementoCommand<TempoMap>(map, &before, &map.get_state()));
 	commit_reversible_command ();
 	
 	map.dump (cerr);
@@ -370,7 +370,7 @@ Editor::edit_meter_section (MeterSection* section)
         XMLNode &before = session->tempo_map().get_state();
 	session->tempo_map().replace_meter (*section, Meter (bpb, note_type));
         XMLNode &after = session->tempo_map().get_state();
-	session->add_command(new MementoCommand<TempoMap>(session->tempo_map(), before, after));
+	session->add_command(new MementoCommand<TempoMap>(session->tempo_map(), &before, &after));
 	commit_reversible_command ();
 }
 
@@ -400,7 +400,7 @@ Editor::edit_tempo_section (TempoSection* section)
 	session->tempo_map().replace_tempo (*section, Tempo (bpm));
 	session->tempo_map().move_tempo (*section, when);
         XMLNode &after = session->tempo_map().get_state();
-	session->add_command (new MementoCommand<TempoMap>(session->tempo_map(), before, after));
+	session->add_command (new MementoCommand<TempoMap>(session->tempo_map(), &before, &after));
 	commit_reversible_command ();
 }
 
@@ -449,7 +449,7 @@ Editor::real_remove_tempo_marker (TempoSection *section)
 	XMLNode &before = session->tempo_map().get_state();
 	session->tempo_map().remove_tempo (*section);
 	XMLNode &after = session->tempo_map().get_state();
-	session->add_command(new MementoCommand<TempoMap>(session->tempo_map(), before, after));
+	session->add_command(new MementoCommand<TempoMap>(session->tempo_map(), &before, &after));
 	commit_reversible_command ();
 
 	return FALSE;
@@ -483,7 +483,7 @@ Editor::real_remove_meter_marker (MeterSection *section)
 	XMLNode &before = session->tempo_map().get_state();
 	session->tempo_map().remove_meter (*section);
 	XMLNode &after = session->tempo_map().get_state();
-	session->add_command(new MementoCommand<TempoMap>(session->tempo_map(), before, after));
+	session->add_command(new MementoCommand<TempoMap>(session->tempo_map(), &before, &after));
 	commit_reversible_command ();
 	return FALSE;
 }
diff --git a/gtk2_ardour/editor_timefx.cc b/gtk2_ardour/editor_timefx.cc
index 3fe0023d07..caa9698b8c 100644
--- a/gtk2_ardour/editor_timefx.cc
+++ b/gtk2_ardour/editor_timefx.cc
@@ -188,7 +188,7 @@ Editor::do_timestretch (TimeStretchDialog& dialog)
 			continue;
 		}
 	
-		if ((playlist = t->diskstream().playlist()) == 0) {
+		if ((playlist = t->diskstream()->playlist()) == 0) {
 			i = tmp;
 			continue;
 		}
@@ -210,7 +210,7 @@ Editor::do_timestretch (TimeStretchDialog& dialog)
 		XMLNode &before = playlist->get_state();
 		playlist->replace_region (region, *new_region, region.position());
 		XMLNode &after = playlist->get_state();
-		session->add_command (new MementoCommand<Playlist>(*playlist, before, after));
+		session->add_command (new MementoCommand<Playlist>(*playlist, &before, &after));
 
 		i = tmp;
 	}
diff --git a/gtk2_ardour/gain_automation_time_axis.cc b/gtk2_ardour/gain_automation_time_axis.cc
index c86c1390f3..47657e3292 100644
--- a/gtk2_ardour/gain_automation_time_axis.cc
+++ b/gtk2_ardour/gain_automation_time_axis.cc
@@ -67,7 +67,7 @@ GainAutomationTimeAxisView::add_automation_event (ArdourCanvas::Item* item, GdkE
         XMLNode &before = curve.get_state();
 	curve.add (when, y);
         XMLNode &after = curve.get_state();
-        _session.add_command(new MementoCommand<ARDOUR::Curve>(curve, before, after));
+        _session.add_command(new MementoCommand<ARDOUR::Curve>(curve, &before, &after));
 	_session.commit_reversible_command ();
 	_session.set_dirty ();
 }
diff --git a/gtk2_ardour/location_ui.cc b/gtk2_ardour/location_ui.cc
index deb4c1da36..12e7079de2 100644
--- a/gtk2_ardour/location_ui.cc
+++ b/gtk2_ardour/location_ui.cc
@@ -658,7 +658,7 @@ gint LocationUI::do_location_remove (ARDOUR::Location *loc)
 	XMLNode &before = session->locations()->get_state();
 	session->locations()->remove (loc);
 	XMLNode &after = session->locations()->get_state();
-	session->add_command(new MementoCommand<Locations>(*(session->locations()), before, after));
+	session->add_command(new MementoCommand<Locations>(*(session->locations()), &before, &after));
 	session->commit_reversible_command ();
 
 	return FALSE;
@@ -777,7 +777,7 @@ LocationUI::add_new_location()
 		XMLNode &before = session->locations()->get_state();
 		session->locations()->add (location, true);
 		XMLNode &after = session->locations()->get_state();
-		session->add_command (new MementoCommand<Locations>(*(session->locations()), before, after));
+		session->add_command (new MementoCommand<Locations>(*(session->locations()), &before, &after));
 		session->commit_reversible_command ();
 	}
 	
@@ -794,7 +794,7 @@ LocationUI::add_new_range()
 		XMLNode &before = session->locations()->get_state();
 		session->locations()->add (location, true);
 		XMLNode &after = session->locations()->get_state();
-		session->add_command (new MementoCommand<Locations>(*(session->locations()), before, after));
+		session->add_command (new MementoCommand<Locations>(*(session->locations()), &before, &after));
 		session->commit_reversible_command ();
 	}
 }
diff --git a/gtk2_ardour/midi_streamview.cc b/gtk2_ardour/midi_streamview.cc
index f422005a5d..47148446eb 100644
--- a/gtk2_ardour/midi_streamview.cc
+++ b/gtk2_ardour/midi_streamview.cc
@@ -163,7 +163,8 @@ MidiStreamView::setup_rec_box ()
 
 				MidiRegion::SourceList sources;
 
-				MidiDiskstream* mds = dynamic_cast<MidiDiskstream*>(_trackview.get_diskstream());
+				// FIXME
+				boost::shared_ptr<MidiDiskstream> mds = boost::dynamic_pointer_cast<MidiDiskstream>(_trackview.get_diskstream());
 				assert(mds);
 
 				sources.push_back((Source*)mds->write_source());
@@ -189,8 +190,8 @@ MidiStreamView::setup_rec_box ()
 			/* start a new rec box */
 
 			MidiTrack* mt = _trackview.midi_track(); /* we know what it is already */
-			MidiDiskstream& ds = mt->midi_diskstream();
-			jack_nframes_t frame_pos = ds.current_capture_start ();
+			boost::shared_ptr<MidiDiskstream> ds = mt->midi_diskstream();
+			jack_nframes_t frame_pos = ds->current_capture_start ();
 			gdouble xstart = _trackview.editor.frame_to_pixel (frame_pos);
 			gdouble xend;
 			uint32_t fill_color;
diff --git a/gtk2_ardour/mixer_ui.cc b/gtk2_ardour/mixer_ui.cc
index c2eb588b2f..84fade5472 100644
--- a/gtk2_ardour/mixer_ui.cc
+++ b/gtk2_ardour/mixer_ui.cc
@@ -251,38 +251,42 @@ Mixer_UI::show_window ()
 }
 
 void
-Mixer_UI::add_strip (boost::shared_ptr<Route> route)
+Mixer_UI::add_strip (Session::RouteList& routes)
 {
-	ENSURE_GUI_THREAD(bind (mem_fun(*this, &Mixer_UI::add_strip), route));
+	ENSURE_GUI_THREAD(bind (mem_fun(*this, &Mixer_UI::add_strip), routes));
 	
 	MixerStrip* strip;
 
-	if (route->hidden()) {
-		return;
-	}
-
-	strip = new MixerStrip (*this, *session, route);
-	strips.push_back (strip);
-
-	strip->set_width (_strip_width);
-	show_strip (strip);
-
-	no_track_list_redisplay = true;
-
-	TreeModel::Row row = *(track_model->append());
-	row[track_columns.text] = route->name();
-
-	row[track_columns.visible] = true;
-	row[track_columns.route] = route;
-	row[track_columns.strip] = strip;
-
-	no_track_list_redisplay = false;
-	redisplay_track_list ();
-
-	route->name_changed.connect (bind (mem_fun(*this, &Mixer_UI::strip_name_changed), strip));
-	strip->GoingAway.connect (bind (mem_fun(*this, &Mixer_UI::remove_strip), strip));
+	for (Session::RouteList::iterator x = routes.begin(); x != routes.end(); ++x) {
+		boost::shared_ptr<Route> route = (*x);
 
-	strip->signal_button_release_event().connect (bind (mem_fun(*this, &Mixer_UI::strip_button_release_event), strip));
+		if (route->hidden()) {
+			return;
+		}
+		
+		strip = new MixerStrip (*this, *session, route);
+		strips.push_back (strip);
+		
+		strip->set_width (_strip_width);
+		show_strip (strip);
+		
+		no_track_list_redisplay = true;
+		
+		TreeModel::Row row = *(track_model->append());
+		row[track_columns.text] = route->name();
+		
+		row[track_columns.visible] = true;
+		row[track_columns.route] = route;
+		row[track_columns.strip] = strip;
+		
+		no_track_list_redisplay = false;
+		redisplay_track_list ();
+		
+		route->name_changed.connect (bind (mem_fun(*this, &Mixer_UI::strip_name_changed), strip));
+		strip->GoingAway.connect (bind (mem_fun(*this, &Mixer_UI::remove_strip), strip));
+		
+		strip->signal_button_release_event().connect (bind (mem_fun(*this, &Mixer_UI::strip_button_release_event), strip));
+	}
 }
 
 void
@@ -623,9 +627,7 @@ Mixer_UI::initial_track_display ()
 
 	track_model->clear ();
 
-	for (Session::RouteList::iterator i = copy.begin(); i != copy.end(); ++i) {
-		add_strip (*i);
-	}
+	add_strip (copy);
 
 	no_track_list_redisplay = false;
 
diff --git a/gtk2_ardour/mixer_ui.h b/gtk2_ardour/mixer_ui.h
index 6fe4120427..77021dc8fe 100644
--- a/gtk2_ardour/mixer_ui.h
+++ b/gtk2_ardour/mixer_ui.h
@@ -111,7 +111,7 @@ class Mixer_UI : public Gtk::Window
 
 	bool strip_scroller_button_release (GdkEventButton*);
 
-	void add_strip (boost::shared_ptr<ARDOUR::Route>);
+	void add_strip (ARDOUR::Session::RouteList&);
 	void remove_strip (MixerStrip *);
 
 	void hide_all_strips (bool with_select);
diff --git a/gtk2_ardour/pan_automation_time_axis.cc b/gtk2_ardour/pan_automation_time_axis.cc
index ec884151b5..bbd4b3b06c 100644
--- a/gtk2_ardour/pan_automation_time_axis.cc
+++ b/gtk2_ardour/pan_automation_time_axis.cc
@@ -92,7 +92,7 @@ PanAutomationTimeAxisView::add_automation_event (ArdourCanvas::Item* item, GdkEv
 	XMLNode &before = alist.get_state();
 	alist.add (when, y);
 	XMLNode &after = alist.get_state();
-        _session.add_command(new MementoCommand<AutomationList>(alist, before, after));
+        _session.add_command(new MementoCommand<AutomationList>(alist, &before, &after));
 	_session.commit_reversible_command ();
 	_session.set_dirty ();
 }
diff --git a/gtk2_ardour/playlist_selector.cc b/gtk2_ardour/playlist_selector.cc
index 8eaac7cb9d..68227d193c 100644
--- a/gtk2_ardour/playlist_selector.cc
+++ b/gtk2_ardour/playlist_selector.cc
@@ -90,7 +90,7 @@ void
 PlaylistSelector::show_for (RouteUI* ruix)
 {
 	vector<const char*> item;
-	Diskstream* this_ds;
+	boost::shared_ptr<Diskstream> this_ds;
 	string str;
 
 	rui = ruix;
@@ -116,7 +116,7 @@ PlaylistSelector::show_for (RouteUI* ruix)
 	
 	for (DSPL_Map::iterator x = dspl_map.begin(); x != dspl_map.end(); ++x) {
 
-		Diskstream* ds = session->diskstream_by_id (x->first);
+		boost::shared_ptr<Diskstream> ds = session->diskstream_by_id (x->first);
 
 		if (ds == 0) {
 			continue;
@@ -243,7 +243,7 @@ PlaylistSelector::selection_changed ()
 			return;
 		}
 		
-		at->diskstream().use_playlist (apl);
+		at->diskstream()->use_playlist (apl);
 
 		hide ();
 	}
diff --git a/gtk2_ardour/redirect_automation_time_axis.cc b/gtk2_ardour/redirect_automation_time_axis.cc
index e527fd1d5e..f1e8eae9eb 100644
--- a/gtk2_ardour/redirect_automation_time_axis.cc
+++ b/gtk2_ardour/redirect_automation_time_axis.cc
@@ -102,7 +102,7 @@ RedirectAutomationTimeAxisView::add_automation_event (ArdourCanvas::Item* item,
                 XMLNode &before = alist.get_state();
 		alist.add (when, y);
                 XMLNode &after = alist.get_state();
-                _session.add_command(new MementoCommand<AutomationList>(alist, before, after));
+                _session.add_command(new MementoCommand<AutomationList>(alist, &before, &after));
 		_session.commit_reversible_command ();
 		_session.set_dirty ();
 	}
diff --git a/gtk2_ardour/region_gain_line.cc b/gtk2_ardour/region_gain_line.cc
index 0a4a3d29ea..e2b1d6c826 100644
--- a/gtk2_ardour/region_gain_line.cc
+++ b/gtk2_ardour/region_gain_line.cc
@@ -48,7 +48,7 @@ AudioRegionGainLine::start_drag (ControlPoint* cp, float fraction)
 {
 	AutomationLine::start_drag(cp,fraction);
 	if (!rv.audio_region().envelope_active()) {
-                trackview.session().add_command(new MementoUndoCommand<AudioRegion>(rv.audio_region(), rv.audio_region().get_state()));
+                trackview.session().add_command(new MementoCommand<AudioRegion>(rv.audio_region(), &rv.audio_region().get_state(), 0));
                 rv.audio_region().set_envelope_active(false);
 	}
 }
@@ -68,12 +68,12 @@ AudioRegionGainLine::remove_point (ControlPoint& cp)
                 XMLNode &before = rv.audio_region().get_state();
 		rv.audio_region().set_envelope_active(true);
                 XMLNode &after = rv.audio_region().get_state();
-                trackview.session().add_command(new MementoCommand<AudioRegion>(rv.audio_region(), before, after));
+                trackview.session().add_command(new MementoCommand<AudioRegion>(rv.audio_region(), &before, &after));
 	}
 
 	alist.erase (mr.start, mr.end);
 
-	trackview.editor.current_session()->add_command (new MementoCommand<AudioRegionGainLine>(*this, before, get_state()));
+	trackview.editor.current_session()->add_command (new MementoCommand<AudioRegionGainLine>(*this, &before, &get_state()));
 	trackview.editor.current_session()->commit_reversible_command ();
 	trackview.editor.current_session()->set_dirty ();
 }
@@ -83,7 +83,7 @@ AudioRegionGainLine::end_drag (ControlPoint* cp)
 {
 	if (!rv.audio_region().envelope_active()) {
 		rv.audio_region().set_envelope_active(true);
-                trackview.session().add_command(new MementoRedoCommand<AudioRegion>(rv.audio_region(), rv.audio_region().get_state()));
+                trackview.session().add_command(new MementoCommand<AudioRegion>(rv.audio_region(), 0, &rv.audio_region().get_state()));
 	}
 	AutomationLine::end_drag(cp);
 }
diff --git a/gtk2_ardour/route_params_ui.cc b/gtk2_ardour/route_params_ui.cc
index 8d8efad8a2..c23ed272e1 100644
--- a/gtk2_ardour/route_params_ui.cc
+++ b/gtk2_ardour/route_params_ui.cc
@@ -159,22 +159,26 @@ RouteParams_UI::~RouteParams_UI ()
 }
 
 void
-RouteParams_UI::add_route (boost::shared_ptr<Route> route)
+RouteParams_UI::add_routes (Session::RouteList& routes)
 {
-	ENSURE_GUI_THREAD(bind (mem_fun(*this, &RouteParams_UI::add_route), route));
+	ENSURE_GUI_THREAD(bind (mem_fun(*this, &RouteParams_UI::add_routes), routes));
 	
-	if (route->hidden()) {
-		return;
-	}
-
-	TreeModel::Row row = *(route_display_model->append());
-	row[route_display_columns.text] = route->name();
-	row[route_display_columns.route] = route;
+	for (Session::RouteList::iterator x = routes.begin(); x != routes.end(); ++x) {
+		boost::shared_ptr<Route> route = (*x);
 
-	//route_select_list.rows().back().select ();
-	
-	route->name_changed.connect (bind (mem_fun(*this, &RouteParams_UI::route_name_changed), route));
-	route->GoingAway.connect (bind (mem_fun(*this, &RouteParams_UI::route_removed), route));
+		if (route->hidden()) {
+			return;
+		}
+		
+		TreeModel::Row row = *(route_display_model->append());
+		row[route_display_columns.text] = route->name();
+		row[route_display_columns.route] = route;
+		
+		//route_select_list.rows().back().select ();
+		
+		route->name_changed.connect (bind (mem_fun(*this, &RouteParams_UI::route_name_changed), route));
+		route->GoingAway.connect (bind (mem_fun(*this, &RouteParams_UI::route_removed), route));
+	}
 }
 
 
@@ -355,9 +359,10 @@ RouteParams_UI::set_session (Session *sess)
 	route_display_model->clear();
 
 	if (session) {
-		session->foreach_route (this, &RouteParams_UI::add_route);
+		boost::shared_ptr<Session::RouteList> r = session->get_routes();
+		add_routes (*r);
 		session->going_away.connect (mem_fun(*this, &ArdourDialog::session_gone));
-		session->RouteAdded.connect (mem_fun(*this, &RouteParams_UI::add_route));
+		session->RouteAdded.connect (mem_fun(*this, &RouteParams_UI::add_routes));
 		start_updating ();
 	} else {
 		stop_updating ();
diff --git a/gtk2_ardour/route_params_ui.h b/gtk2_ardour/route_params_ui.h
index 5f487d6e5c..eff31023f7 100644
--- a/gtk2_ardour/route_params_ui.h
+++ b/gtk2_ardour/route_params_ui.h
@@ -159,7 +159,7 @@ class RouteParams_UI : public ArdourDialog
 	Glib::RefPtr<Gtk::ListStore> route_display_model;
 
 	
-	void add_route (boost::shared_ptr<ARDOUR::Route>);
+	void add_routes (ARDOUR::Session::RouteList&);
 
 	void route_name_changed (void *src, boost::shared_ptr<ARDOUR::Route> route);
 	void route_removed (boost::shared_ptr<ARDOUR::Route> route);
diff --git a/gtk2_ardour/route_time_axis.cc b/gtk2_ardour/route_time_axis.cc
index e2e1fb2149..e7a6df2f27 100644
--- a/gtk2_ardour/route_time_axis.cc
+++ b/gtk2_ardour/route_time_axis.cc
@@ -728,7 +728,7 @@ RouteTimeAxisView::rename_current_playlist ()
 	ArdourPrompter prompter (true);
 	string name;
 
-	Diskstream *const ds = get_diskstream();
+	boost::shared_ptr<Diskstream> ds = get_diskstream();
 	if (!ds || ds->destructive())
 		return;
 
@@ -759,7 +759,7 @@ RouteTimeAxisView::use_copy_playlist (bool prompt)
 {
 	string name;
 	
-	Diskstream *const ds = get_diskstream();
+	boost::shared_ptr<Diskstream> ds = get_diskstream();
 	if (!ds || ds->destructive())
 		return;
 
@@ -800,7 +800,7 @@ RouteTimeAxisView::use_new_playlist (bool prompt)
 {
 	string name;
 	
-	Diskstream *const ds = get_diskstream();
+	boost::shared_ptr<Diskstream> ds = get_diskstream();
 	if (!ds || ds->destructive())
 		return;
 
@@ -838,7 +838,7 @@ RouteTimeAxisView::use_new_playlist (bool prompt)
 void
 RouteTimeAxisView::clear_playlist ()
 {
-	Diskstream *const ds = get_diskstream();
+	boost::shared_ptr<Diskstream> ds = get_diskstream();
 	if (!ds || ds->destructive())
 		return;
 
@@ -878,8 +878,7 @@ RouteTimeAxisView::selection_click (GdkEventButton* ev)
 
 	switch (Keyboard::selection_type (ev->state)) {
 	case Selection::Toggle:
-		/* XXX this is not right */
-		editor.get_selection().add (*tracks);
+		editor.get_selection().toggle (*tracks);
 		break;
 		
 	case Selection::Set:
@@ -964,7 +963,7 @@ RouteTimeAxisView::name() const
 Playlist *
 RouteTimeAxisView::playlist () const 
 {
-	Diskstream *ds;
+	boost::shared_ptr<Diskstream> ds;
 
 	if ((ds = get_diskstream()) != 0) {
 		return ds->playlist(); 
@@ -1014,7 +1013,7 @@ RouteTimeAxisView::hide_click ()
 Region*
 RouteTimeAxisView::find_next_region (jack_nframes_t pos, RegionPoint point, int32_t dir)
 {
-	Diskstream *stream;
+	boost::shared_ptr<Diskstream> stream;
 	Playlist *playlist;
 
 	if ((stream = get_diskstream()) != 0 && (playlist = stream->playlist()) != 0) {
@@ -1028,7 +1027,7 @@ bool
 RouteTimeAxisView::cut_copy_clear (Selection& selection, CutCopyOp op)
 {
 	Playlist* what_we_got;
-	Diskstream* ds = get_diskstream();
+	boost::shared_ptr<Diskstream> ds = get_diskstream();
 	Playlist* playlist;
 	bool ret = false;
 
@@ -1054,7 +1053,7 @@ RouteTimeAxisView::cut_copy_clear (Selection& selection, CutCopyOp op)
 	case Cut:
 		if ((what_we_got = playlist->cut (time)) != 0) {
 			editor.get_cut_buffer().add (what_we_got);
-			_session.add_command( new MementoCommand<Playlist>(*playlist, before, playlist->get_state()));
+			_session.add_command( new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
 			ret = true;
 		}
 		break;
@@ -1066,7 +1065,7 @@ RouteTimeAxisView::cut_copy_clear (Selection& selection, CutCopyOp op)
 
 	case Clear:
 		if ((what_we_got = playlist->cut (time)) != 0) {
-			_session.add_command( new MementoCommand<Playlist>(*playlist, before, playlist->get_state()));
+			_session.add_command( new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
 			what_we_got->unref ();
 			ret = true;
 		}
@@ -1097,7 +1096,7 @@ RouteTimeAxisView::paste (jack_nframes_t pos, float times, Selection& selection,
 	
 	XMLNode &before = playlist->get_state();
 	playlist->paste (**p, pos, times);
-	_session.add_command( new MementoCommand<Playlist>(*playlist, before, playlist->get_state()));
+	_session.add_command( new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
 
 	return true;
 }
diff --git a/gtk2_ardour/route_ui.cc b/gtk2_ardour/route_ui.cc
index 6b3c2a820c..3ede0bc1c7 100644
--- a/gtk2_ardour/route_ui.cc
+++ b/gtk2_ardour/route_ui.cc
@@ -76,7 +76,7 @@ RouteUI::RouteUI (boost::shared_ptr<ARDOUR::Route> rt, ARDOUR::Session& sess, co
 	if (is_track()) {
 		boost::shared_ptr<Track> t = boost::dynamic_pointer_cast<Track>(_route);
 
-		t->diskstream().RecordEnableChanged.connect (mem_fun (*this, &RouteUI::route_rec_enable_changed));
+		t->diskstream()->RecordEnableChanged.connect (mem_fun (*this, &RouteUI::route_rec_enable_changed));
 
 		_session.RecordStateChanged.connect (mem_fun (*this, &RouteUI::session_rec_enable_changed));
 
@@ -577,7 +577,7 @@ RouteUI::reversibly_apply_route_boolean (string name, void (Route::*func)(bool,
         XMLNode &before = _route->get_state();
         bind(mem_fun(*_route, func), yn, arg)();
         XMLNode &after = _route->get_state();
-        _session.add_command (new MementoCommand<Route>(*_route, before, after));
+        _session.add_command (new MementoCommand<Route>(*_route, &before, &after));
 	_session.commit_reversible_command ();
 }
 
@@ -588,7 +588,7 @@ RouteUI::reversibly_apply_audio_track_boolean (string name, void (AudioTrack::*f
         XMLNode &before = audio_track()->get_state();
 	bind (mem_fun (*audio_track(), func), yn, arg)();
         XMLNode &after = audio_track()->get_state();
-	_session.add_command (new MementoCommand<AudioTrack>(*audio_track(), before, after));
+	_session.add_command (new MementoCommand<AudioTrack>(*audio_track(), &before, &after));
 	_session.commit_reversible_command ();
 }
 
@@ -599,7 +599,7 @@ RouteUI::reversibly_apply_track_boolean (string name, void (Track::*func)(bool,
         XMLNode &before = track()->get_state();
 	bind (mem_fun (*track(), func), yn, arg)();
         XMLNode &after = track()->get_state();
-	_session.add_command (new MementoCommand<Track>(*track(), before, after));
+	_session.add_command (new MementoCommand<Track>(*track(), &before, &after));
 	_session.commit_reversible_command ();
 }
 
@@ -746,7 +746,6 @@ void
 RouteUI::route_removed ()
 {
 	ENSURE_GUI_THREAD(mem_fun (*this, &RouteUI::route_removed));
-	
 	delete this;
 }
 
@@ -930,15 +929,15 @@ RouteUI::midi_track() const
 	return dynamic_cast<MidiTrack*>(_route.get());
 }
 
-Diskstream*
+boost::shared_ptr<Diskstream>
 RouteUI::get_diskstream () const
 {
 	boost::shared_ptr<Track> t;
 
 	if ((t = boost::dynamic_pointer_cast<Track>(_route)) != 0) {
-		return &t->diskstream();
+		return t->diskstream();
 	} else {
-		return 0;
+		return boost::shared_ptr<Diskstream> ((Diskstream*) 0);
 	}
 }
 
diff --git a/gtk2_ardour/route_ui.h b/gtk2_ardour/route_ui.h
index 156063a8e5..b01d7d41cb 100644
--- a/gtk2_ardour/route_ui.h
+++ b/gtk2_ardour/route_ui.h
@@ -60,7 +60,7 @@ class RouteUI : public virtual AxisView
 	ARDOUR::AudioTrack* audio_track() const;
 	ARDOUR::MidiTrack*  midi_track() const;
 	
-	ARDOUR::Diskstream* get_diskstream() const;
+	boost::shared_ptr<ARDOUR::Diskstream> get_diskstream() const;
 
 	string name() const;
 
diff --git a/gtk2_ardour/selection.cc b/gtk2_ardour/selection.cc
index 086d878994..aa7fdbe30f 100644
--- a/gtk2_ardour/selection.cc
+++ b/gtk2_ardour/selection.cc
@@ -180,6 +180,14 @@ Selection::toggle (Playlist* pl)
 }
 
 void
+Selection::toggle (const list<TimeAxisView*>& track_list)
+{
+	for (list<TimeAxisView*>::const_iterator i = track_list.begin(); i != track_list.end(); ++i) {
+		toggle ( (*i) );
+	}
+}
+
+void
 Selection::toggle (TimeAxisView* track)
 {
 	TrackSelection::iterator i;
@@ -616,6 +624,7 @@ Selection::set (list<Selectable*>& selectables)
 	add (selectables);
 }
 
+
 void
 Selection::add (list<Selectable*>& selectables)
 {
diff --git a/gtk2_ardour/streamview.cc b/gtk2_ardour/streamview.cc
index 82f941f9bd..ff51ca4b9f 100644
--- a/gtk2_ardour/streamview.cc
+++ b/gtk2_ardour/streamview.cc
@@ -207,7 +207,7 @@ StreamView::undisplay_diskstream ()
 }
 
 void
-StreamView::display_diskstream (Diskstream *ds)
+StreamView::display_diskstream (boost::shared_ptr<Diskstream> ds)
 {
 	playlist_change_connection.disconnect();
 	playlist_changed (ds);
@@ -225,7 +225,7 @@ StreamView::playlist_modified ()
 }
 
 void
-StreamView::playlist_changed (Diskstream *ds)
+StreamView::playlist_changed (boost::shared_ptr<Diskstream> ds)
 {
 	ENSURE_GUI_THREAD (bind (mem_fun (*this, &StreamView::playlist_changed), ds));
 
@@ -264,9 +264,7 @@ StreamView::diskstream_changed ()
 	Track *t;
 
 	if ((t = _trackview.track()) != 0) {
-		Diskstream& ds = t->diskstream();
-		/* XXX grrr: when will SigC++ allow me to bind references? */
-		Gtkmm2ext::UI::instance()->call_slot (bind (mem_fun (*this, &StreamView::display_diskstream), &ds));
+		Gtkmm2ext::UI::instance()->call_slot (bind (mem_fun (*this, &StreamView::display_diskstream), t->diskstream()));
 	} else {
 		Gtkmm2ext::UI::instance()->call_slot (mem_fun (*this, &StreamView::undisplay_diskstream));
 	}
diff --git a/gtk2_ardour/streamview.h b/gtk2_ardour/streamview.h
index bee51e8835..fb49433cce 100644
--- a/gtk2_ardour/streamview.h
+++ b/gtk2_ardour/streamview.h
@@ -111,13 +111,13 @@ protected:
 	virtual void remove_region_view (ARDOUR::Region* );
 	void         remove_rec_region (ARDOUR::Region*);
 
-	void         display_diskstream (ARDOUR::Diskstream* );
+	void         display_diskstream (boost::shared_ptr<ARDOUR::Diskstream>);
 	virtual void undisplay_diskstream ();
 	virtual void redisplay_diskstream () = 0;
 	void         diskstream_changed ();
 	
 	void         playlist_state_changed (ARDOUR::Change);
-	virtual void playlist_changed (ARDOUR::Diskstream* );
+	virtual void playlist_changed (boost::shared_ptr<ARDOUR::Diskstream>);
 	virtual void playlist_modified ();
 	
 	virtual void color_handler (ColorID, uint32_t) = 0;
diff --git a/libs/ardour/ardour/audio_diskstream.h b/libs/ardour/ardour/audio_diskstream.h
index 0cc2079d8e..18f8328cfd 100644
--- a/libs/ardour/ardour/audio_diskstream.h
+++ b/libs/ardour/ardour/audio_diskstream.h
@@ -59,12 +59,10 @@ class AudioDiskstream : public Diskstream
   public:
 	AudioDiskstream (Session &, const string& name, Diskstream::Flag f = Recordable);
 	AudioDiskstream (Session &, const XMLNode&);
+	~AudioDiskstream();
 
 	const PBD::ID& id() const { return _id; }
 
-	// FIXME
-	AudioDiskstream& ref() { _refcnt++; return *this; }
-
 	float playback_buffer_load() const;
 	float capture_buffer_load() const;
 
@@ -176,9 +174,6 @@ class AudioDiskstream : public Diskstream
 
   private:
 
-	/* use unref() to destroy a diskstream */
-	~AudioDiskstream();
-
 	struct ChannelInfo {
 
 		Sample     *playback_wrap_buffer;
diff --git a/libs/ardour/ardour/audio_track.h b/libs/ardour/ardour/audio_track.h
index bca79b0d7d..fe6c88cf7f 100644
--- a/libs/ardour/ardour/audio_track.h
+++ b/libs/ardour/ardour/audio_track.h
@@ -46,7 +46,7 @@ class AudioTrack : public Track
 	int silent_roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nframes_t end_frame, 
 		jack_nframes_t offset, bool can_record, bool rec_monitors_input);
 
-	AudioDiskstream& audio_diskstream() const;
+	boost::shared_ptr<AudioDiskstream> audio_diskstream() const;
 
 	int use_diskstream (string name);
 	int use_diskstream (const PBD::ID& id);
@@ -67,7 +67,7 @@ class AudioTrack : public Track
 	ChanCount n_process_buffers ();
 	
   private:
-	int  set_diskstream (AudioDiskstream&, void *);
+	int  set_diskstream (boost::shared_ptr<AudioDiskstream>, void *);
 	int  deprecated_use_diskstream_connections ();
 	void set_state_part_two ();
 	void set_state_part_three ();
diff --git a/libs/ardour/ardour/audioengine.h b/libs/ardour/ardour/audioengine.h
index 570ad2830d..db814bbb5f 100644
--- a/libs/ardour/ardour/audioengine.h
+++ b/libs/ardour/ardour/audioengine.h
@@ -31,6 +31,8 @@
 
 #include <glibmm/thread.h>
 
+#include <pbd/rcu.h>
+
 #include <ardour/ardour.h>
 #include <jack/jack.h>
 #include <jack/transport.h>
@@ -119,6 +121,9 @@ class AudioEngine : public sigc::trackable
 	uint32_t n_physical_outputs () const;
 	uint32_t n_physical_inputs () const;
 
+	void get_physical_outputs (std::vector<std::string>&);
+	void get_physical_inputs (std::vector<std::string>&);
+
 	std::string get_nth_physical_output (DataType type, uint32_t n) {
 		return get_nth_physical (type, n, JackPortIsInput);
 	}
@@ -187,7 +192,6 @@ class AudioEngine : public sigc::trackable
 	ARDOUR::Session      *session;
 	jack_client_t       *_jack;
 	std::string           jack_client_name;
-	Glib::Mutex           port_lock;
 	Glib::Mutex           _process_lock;
 	Glib::Mutex           session_remove_lock;
     Glib::Cond            session_removed;
@@ -206,7 +210,7 @@ class AudioEngine : public sigc::trackable
 	int                  _usecs_per_cycle;
 
 	typedef std::set<Port*> Ports;
-	Ports ports;
+	SerializedRCUManager<Ports> ports;
 
 	int    process_callback (jack_nframes_t nframes);
 	void   remove_all_ports ();
diff --git a/libs/ardour/ardour/automation_event.h b/libs/ardour/ardour/automation_event.h
index 5864de73c6..dad94161d0 100644
--- a/libs/ardour/ardour/automation_event.h
+++ b/libs/ardour/ardour/automation_event.h
@@ -183,6 +183,8 @@ class AutomationList : public StateManager, public Stateful
 		}
 	};
 
+        static sigc::signal<void, AutomationList*> AutomationListCreated;
+
   protected:
         PBD::ID _id;
 	struct State : public ARDOUR::StateManager::State {
diff --git a/libs/ardour/ardour/curve.h b/libs/ardour/ardour/curve.h
index df632c5171..87893ca260 100644
--- a/libs/ardour/ardour/curve.h
+++ b/libs/ardour/ardour/curve.h
@@ -59,6 +59,8 @@ class Curve : public AutomationList
 	AutomationEventList::iterator closest_control_point_after (double xval);
 
 	void solve ();
+
+        static sigc::signal<void, Curve*> CurveCreated;
 		
   protected:
 	ControlEvent* point_factory (double,double) const;
diff --git a/libs/ardour/ardour/diskstream.h b/libs/ardour/ardour/diskstream.h
index 0803436913..858ed1af6f 100644
--- a/libs/ardour/ardour/diskstream.h
+++ b/libs/ardour/ardour/diskstream.h
@@ -34,6 +34,7 @@
 #include <pbd/fastlog.h>
 #include <pbd/ringbufferNPT.h>
 #include <pbd/stateful.h>
+#include <pbd/destructible.h>
 
 #include <ardour/ardour.h>
 #include <ardour/configuration.h>
@@ -43,7 +44,6 @@
 #include <ardour/port.h>
 #include <ardour/utils.h>
 
-
 struct tm;
 
 namespace ARDOUR {
@@ -54,7 +54,7 @@ class Session;
 class Playlist;
 class IO;
 
-class Diskstream : public Stateful, public sigc::trackable
+ class Diskstream : public Stateful, public sigc::trackable, public PBD::Destructible
 {	
   public:
 	enum Flag {
@@ -63,16 +63,16 @@ class Diskstream : public Stateful, public sigc::trackable
 		Destructive = 0x4
 	};
 
+	Diskstream (Session &, const string& name, Flag f = Recordable);
+	Diskstream (Session &, const XMLNode&);
+	virtual ~Diskstream();
+
 	string      name () const { return _name; }
 	virtual int set_name (string str);
 
 	ARDOUR::IO* io() const { return _io; }
 	void set_io (ARDOUR::IO& io);
 
-	Diskstream& ref()          { _refcnt++; return *this; }
-	void        unref()        { if (_refcnt) _refcnt--; if (_refcnt == 0) delete this; }
-	uint32_t    refcnt() const { return _refcnt; }
-
 	virtual float playback_buffer_load() const = 0;
 	virtual float capture_buffer_load() const = 0;
 
@@ -147,15 +147,11 @@ class Diskstream : public Stateful, public sigc::trackable
 
 	static sigc::signal<void>                DiskOverrun;
 	static sigc::signal<void>                DiskUnderrun;
-	static sigc::signal<void,Diskstream*>    DiskstreamCreated; // XXX use a ref with sigc2
 	static sigc::signal<void,list<Source*>*> DeleteSources;
 
   protected:
 	friend class Session;
 
-	Diskstream (Session &, const string& name, Flag f = Recordable);
-	Diskstream (Session &, const XMLNode&);
-
 	/* the Session is the only point of access for these because they require
 	 * that the Session is "inactive" while they are called.
 	 */
@@ -186,9 +182,6 @@ class Diskstream : public Stateful, public sigc::trackable
 
 	//private:
 	
-	/** Use unref() to destroy a diskstream */
-	virtual ~Diskstream();
-
 	enum TransitionType {
 		CaptureStart = 0,
 		CaptureEnd
@@ -303,8 +296,6 @@ class Diskstream : public Stateful, public sigc::trackable
 	jack_nframes_t scrub_buffer_size;
 	jack_nframes_t scrub_offset;
 
-	uint32_t _refcnt;
-
 	sigc::connection ports_created_c;
 	sigc::connection plmod_connection;
 	sigc::connection plstate_connection;
diff --git a/libs/ardour/ardour/location.h b/libs/ardour/ardour/location.h
index ff953d1d78..beae4a6e07 100644
--- a/libs/ardour/ardour/location.h
+++ b/libs/ardour/ardour/location.h
@@ -149,6 +149,7 @@ class Locations : public Stateful, public StateManager
 	XMLNode& get_state (void);
 	int set_state (const XMLNode&);
         PBD::ID id() { return _id; }
+        Location *get_location_by_id(PBD::ID);
 
 	Location* auto_loop_location () const;
 	Location* auto_punch_location () const;
diff --git a/libs/ardour/ardour/midi_diskstream.h b/libs/ardour/ardour/midi_diskstream.h
index 0e4aed1929..bf64cedd08 100644
--- a/libs/ardour/ardour/midi_diskstream.h
+++ b/libs/ardour/ardour/midi_diskstream.h
@@ -63,6 +63,7 @@ class MidiDiskstream : public Diskstream
   public:
 	MidiDiskstream (Session &, const string& name, Diskstream::Flag f = Recordable);
 	MidiDiskstream (Session &, const XMLNode&);
+	~MidiDiskstream();
 
 	float playback_buffer_load() const;
 	float capture_buffer_load() const;
@@ -116,9 +117,6 @@ class MidiDiskstream : public Diskstream
 
   private:
 
-	/* use unref() to destroy a diskstream */
-	~MidiDiskstream();
-
 	/* The two central butler operations */
 	int do_flush (Session::RunContext context, bool force = false);
 	int do_refill ();
diff --git a/libs/ardour/ardour/midi_ring_buffer.h b/libs/ardour/ardour/midi_ring_buffer.h
index 662f5a8350..e8b499397d 100644
--- a/libs/ardour/ardour/midi_ring_buffer.h
+++ b/libs/ardour/ardour/midi_ring_buffer.h
@@ -148,9 +148,9 @@ MidiRingBuffer::write (const MidiEvent& ev)
 		write_ev->buffer = &_raw_buf[raw_index];
         g_atomic_int_set(&_write_ptr, (priv_write_ptr + 1) % _size);
 		
-		printf("MRB - wrote %xd %d %d with time %u at index %zu (raw index %zu)\n",
-			write_ev->buffer[0], write_ev->buffer[1], write_ev->buffer[2], write_ev->time,
-			priv_write_ptr, raw_index);
+		//printf("MRB - wrote %xd %d %d with time %u at index %zu (raw index %zu)\n",
+		//	write_ev->buffer[0], write_ev->buffer[1], write_ev->buffer[2], write_ev->time,
+		//	priv_write_ptr, raw_index);
 		
 		assert(write_ev->size = ev.size);
 
@@ -176,9 +176,9 @@ MidiRingBuffer::read(MidiBuffer& dst, jack_nframes_t start, jack_nframes_t end)
 		MidiEvent* const read_ev = &_ev_buf[priv_read_ptr];
 		if (time >= start) {
 			dst.push_back(*read_ev);
-			printf("MRB - read %#X %d %d with time %u at index %zu\n",
-				read_ev->buffer[0], read_ev->buffer[1], read_ev->buffer[2], read_ev->time,
-				priv_read_ptr);
+			//printf("MRB - read %#X %d %d with time %u at index %zu\n",
+			//	read_ev->buffer[0], read_ev->buffer[1], read_ev->buffer[2], read_ev->time,
+			//	priv_read_ptr);
 		} else {
 			printf("MRB - SKIPPING - %#X %d %d with time %u at index %zu\n",
 				read_ev->buffer[0], read_ev->buffer[1], read_ev->buffer[2], read_ev->time,
diff --git a/libs/ardour/ardour/midi_track.h b/libs/ardour/ardour/midi_track.h
index 409aa171e9..7c4befe116 100644
--- a/libs/ardour/ardour/midi_track.h
+++ b/libs/ardour/ardour/midi_track.h
@@ -53,7 +53,7 @@ public:
 				     jack_nframes_t nframes, jack_nframes_t offset, bool with_redirects, int declick,
 				     bool meter);
 
-	MidiDiskstream& midi_diskstream() const;
+	boost::shared_ptr<MidiDiskstream> midi_diskstream() const;
 
 	int use_diskstream (string name);
 	int use_diskstream (const PBD::ID& id);
@@ -79,7 +79,7 @@ protected:
 	ChanCount n_process_buffers ();
 
 private:
-	int set_diskstream (MidiDiskstream&);
+	int set_diskstream (boost::shared_ptr<MidiDiskstream> ds);
 
 	void set_state_part_two ();
 	void set_state_part_three ();
diff --git a/libs/ardour/ardour/route.h b/libs/ardour/ardour/route.h
index 107abb7b48..5b9c92dc71 100644
--- a/libs/ardour/ardour/route.h
+++ b/libs/ardour/ardour/route.h
@@ -35,6 +35,7 @@
 #include <pbd/undo.h>
 #include <pbd/stateful.h> 
 #include <pbd/controllable.h>
+#include <pbd/destructible.h>
 
 #include <ardour/ardour.h>
 #include <ardour/io.h>
@@ -55,7 +56,7 @@ enum mute_type {
     MAIN_OUTS =    0x8
 };
 
-class Route : public IO
+ class Route : public IO, public PBD::Destructible
 {
   protected:
 
@@ -192,8 +193,6 @@ class Route : public IO
 	sigc::signal<void>       active_changed;
 	sigc::signal<void,void*> meter_change;
 
-	sigc::signal<void> GoingAway;
-
 	/* gui's call this for their own purposes. */
 
 	sigc::signal<void,std::string,void*> gui_changed;
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 2737d86a3f..eeb905a301 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -285,8 +285,9 @@ class Session : public sigc::trackable, public Stateful
 	BufferSet& get_scratch_buffers (ChanCount count = ChanCount::ZERO);
 	BufferSet& get_send_buffers (ChanCount count = ChanCount::ZERO);
 	
-	Diskstream    *diskstream_by_id (const PBD::ID& id);
-	Diskstream    *diskstream_by_name (string name);
+	void add_diskstream (boost::shared_ptr<Diskstream>);
+	boost::shared_ptr<Diskstream> diskstream_by_id (const PBD::ID& id);
+	boost::shared_ptr<Diskstream> diskstream_by_name (string name);
 
 	bool have_captured() const { return _have_captured; }
 
@@ -296,9 +297,8 @@ class Session : public sigc::trackable, public Stateful
 	uint32_t get_next_diskstream_id() const { return n_diskstreams(); }
 	uint32_t n_diskstreams() const;
 	
-	typedef list<Diskstream *> DiskstreamList;
-	
-	typedef std::list<boost::shared_ptr<Route> > RouteList; 
+	typedef std::list<boost::shared_ptr<Diskstream> > DiskstreamList;
+	typedef std::list<boost::shared_ptr<Route> >      RouteList; 
 	
 	boost::shared_ptr<RouteList> get_routes() const {
 		return routes.reader ();
@@ -317,6 +317,7 @@ class Session : public sigc::trackable, public Stateful
 	template<class T, class A> void foreach_route (T *obj, void (T::*func)(Route&, A), A arg);
 
 	boost::shared_ptr<Route> route_by_name (string);
+	boost::shared_ptr<Route> route_by_id (PBD::ID);
 	boost::shared_ptr<Route> route_by_remote_id (uint32_t id);
 
 	bool route_name_unique (string) const;
@@ -350,7 +351,7 @@ class Session : public sigc::trackable, public Stateful
 	
 	/* Record status signals */
 
-        sigc::signal<void> RecordStateChanged;
+	sigc::signal<void> RecordStateChanged;
 
 	/* Transport mechanism signals */
 
@@ -359,8 +360,7 @@ class Session : public sigc::trackable, public Stateful
 	sigc::signal<void> DurationChanged;
 	sigc::signal<void> HaltOnXrun;
 
-	sigc::signal<void,boost::shared_ptr<Route> > RouteAdded;
-	sigc::signal<void,Diskstream*> DiskstreamAdded;
+	sigc::signal<void,RouteList&> RouteAdded;
 
 	void request_roll ();
 	void request_bounded_roll (jack_nframes_t start, jack_nframes_t end);
@@ -494,6 +494,7 @@ class Session : public sigc::trackable, public Stateful
 	int restore_state (string snapshot_name);
 	int save_template (string template_name);
         int save_history (string snapshot_name = "");
+        int restore_history (string snapshot_name);
 
 	static int rename_template (string old_name, string new_name);
 
@@ -551,11 +552,11 @@ class Session : public sigc::trackable, public Stateful
 
 	/* fundamental operations. duh. */
 
-	boost::shared_ptr<AudioTrack> new_audio_track (int input_channels, int output_channels, TrackMode mode = Normal);
-	boost::shared_ptr<Route>      new_audio_route (int input_channels, int output_channels);
+	std::list<boost::shared_ptr<AudioTrack> > new_audio_track (int input_channels, int output_channels, TrackMode mode = Normal, uint32_t how_many = 1);
+	RouteList new_audio_route (int input_channels, int output_channels, uint32_t how_many);
 	
-	boost::shared_ptr<MidiTrack> new_midi_track (TrackMode mode = Normal);
-	boost::shared_ptr<Route>      new_midi_route ();
+	std::list<boost::shared_ptr<MidiTrack> > new_midi_track (TrackMode mode = Normal, uint32_t how_many = 1);
+	//boost::shared_ptr<Route>     new_midi_route (uint32_t how_many = 1);
 
 	void   remove_route (boost::shared_ptr<Route>);
 	void   resort_routes ();
@@ -735,6 +736,10 @@ class Session : public sigc::trackable, public Stateful
 	sigc::signal<void> NamedSelectionAdded;
 	sigc::signal<void> NamedSelectionRemoved;
 
+        /* Curves and AutomationLists (TODO when they go away) */
+        void add_curve(Curve*);
+        void add_automation_list(AutomationList*);
+
 	/* fade curves */
 
 	float get_default_fade_length () const { return default_fade_msecs; }
@@ -861,6 +866,7 @@ class Session : public sigc::trackable, public Stateful
 
         // these commands are implemented in libs/ardour/session_command.cc
 	Command *memento_command_factory(XMLNode *n);
+        void register_with_memento_command_factory(PBD::ID, Stateful *);
         class GlobalSoloStateCommand : public Command
         {
             GlobalRouteBooleanState before, after;
@@ -1520,17 +1526,16 @@ class Session : public sigc::trackable, public Stateful
 
 	/* disk-streams */
 
-	DiskstreamList  diskstreams; 
-	mutable Glib::RWLock diskstream_lock;
+	SerializedRCUManager<DiskstreamList>  diskstreams; 
+
 	uint32_t dstream_buffer_size;
-	void add_diskstream (Diskstream*);
 	int  load_diskstreams (const XMLNode&);
 
 	/* routes stuff */
 
 	SerializedRCUManager<RouteList>  routes;
 
-	void   add_route (boost::shared_ptr<Route>);
+	void   add_routes (RouteList&, bool save = true);
 	uint32_t destructive_index;
 
 	int load_routes (const XMLNode&);
@@ -1591,7 +1596,7 @@ class Session : public sigc::trackable, public Stateful
 	Playlist *XMLPlaylistFactory (const XMLNode&);
 
 	void playlist_length_changed (Playlist *);
-	void diskstream_playlist_changed (Diskstream *);
+	void diskstream_playlist_changed (boost::shared_ptr<Diskstream>);
 
 	/* NAMED SELECTIONS */
 
@@ -1604,6 +1609,10 @@ class Session : public sigc::trackable, public Stateful
 	NamedSelection *named_selection_factory (string name);
 	NamedSelection *XMLNamedSelectionFactory (const XMLNode&);
 
+        /* CURVES and AUTOMATION LISTS */
+        std::map<PBD::ID, Curve*> curves;
+        std::map<PBD::ID, AutomationList*> automation_lists;
+
 	/* DEFAULT FADE CURVES */
 
 	float default_fade_steepness;
diff --git a/libs/ardour/ardour/track.h b/libs/ardour/ardour/track.h
index 2b317a0299..2e628fa586 100644
--- a/libs/ardour/ardour/track.h
+++ b/libs/ardour/ardour/track.h
@@ -19,6 +19,8 @@
 #ifndef __ardour_track_h__
 #define __ardour_track_h__
 
+#include <boost/shared_ptr.hpp>
+
 #include <ardour/route.h>
 
 namespace ARDOUR {
@@ -50,7 +52,7 @@ class Track : public Route
 
 	bool can_record();
 
-	Diskstream& diskstream() const { return *_diskstream; }
+	boost::shared_ptr<Diskstream> diskstream() const { return _diskstream; }
 
 	virtual int use_diskstream (string name) = 0;
 	virtual int use_diskstream (const PBD::ID& id) = 0;
@@ -97,7 +99,7 @@ class Track : public Route
 
 	virtual ChanCount n_process_buffers () = 0;
 	
-	Diskstream *_diskstream;
+	boost::shared_ptr<Diskstream> _diskstream;
 	MeterPoint  _saved_meter_point;
 	TrackMode   _mode;
 
diff --git a/libs/ardour/audio_diskstream.cc b/libs/ardour/audio_diskstream.cc
index 40c8e3301b..dceaea3f7e 100644
--- a/libs/ardour/audio_diskstream.cc
+++ b/libs/ardour/audio_diskstream.cc
@@ -72,8 +72,6 @@ AudioDiskstream::AudioDiskstream (Session &sess, const string &name, Diskstream:
 	use_new_playlist ();
 
 	in_set_state = false;
-
-	DiskstreamCreated (this); /* EMIT SIGNAL */
 }
 	
 AudioDiskstream::AudioDiskstream (Session& sess, const XMLNode& node)
@@ -93,8 +91,6 @@ AudioDiskstream::AudioDiskstream (Session& sess, const XMLNode& node)
 	if (destructive()) {
 		use_destructive_playlist ();
 	}
-
-	DiskstreamCreated (this); /* EMIT SIGNAL */
 }
 
 void
@@ -1622,8 +1618,8 @@ AudioDiskstream::transport_stopped (struct tm& when, time_t twhen, bool abort_ca
 		}
 
 		_playlist->thaw ();
-                XMLNode &after = _playlist->get_state();
-		_session.add_command (new MementoCommand<Playlist>(*_playlist, before, after));
+		XMLNode &after = _playlist->get_state();
+		_session.add_command (new MementoCommand<Playlist>(*_playlist, &before, &after));
 	}
 
 	mark_write_completed = true;
diff --git a/libs/ardour/audio_track.cc b/libs/ardour/audio_track.cc
index b12b79858e..7a44be9b54 100644
--- a/libs/ardour/audio_track.cc
+++ b/libs/ardour/audio_track.cc
@@ -55,9 +55,10 @@ AudioTrack::AudioTrack (Session& sess, string name, Route::Flag flag, TrackMode
 		dflags = AudioDiskstream::Flag (dflags | AudioDiskstream::Destructive);
 	}
 
-	AudioDiskstream* ds = new AudioDiskstream (_session, name, dflags);
-	
-	set_diskstream (*ds, this);
+	boost::shared_ptr<AudioDiskstream> ds (new AudioDiskstream (_session, name, dflags));
+	_session.add_diskstream (ds);
+
+	set_diskstream (boost::dynamic_pointer_cast<AudioDiskstream> (ds), this);
 }
 
 AudioTrack::AudioTrack (Session& sess, const XMLNode& node)
@@ -73,18 +74,18 @@ AudioTrack::~AudioTrack ()
 int
 AudioTrack::deprecated_use_diskstream_connections ()
 {
-	AudioDiskstream& diskstream = audio_diskstream();
+	boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 
-	if (diskstream.deprecated_io_node == 0) {
+	if (diskstream->deprecated_io_node == 0) {
 		return 0;
 	}
 
 	const XMLProperty* prop;
-	XMLNode& node (*diskstream.deprecated_io_node);
+	XMLNode& node (*diskstream->deprecated_io_node);
 
 	/* don't do this more than once. */
 
-	diskstream.deprecated_io_node = 0;
+	diskstream->deprecated_io_node = 0;
 
 	set_input_minimum (-1);
 	set_input_maximum (-1);
@@ -125,17 +126,13 @@ AudioTrack::deprecated_use_diskstream_connections ()
 }
 
 int
-AudioTrack::set_diskstream (AudioDiskstream& ds, void *src)
+AudioTrack::set_diskstream (boost::shared_ptr<AudioDiskstream> ds, void *src)
 {
-	if (_diskstream) {
-		_diskstream->unref();
-	}
-
-	_diskstream = &ds.ref();
+	_diskstream = ds;
 	_diskstream->set_io (*this);
 	_diskstream->set_destructive (_mode == Destructive);
 
-	if (audio_diskstream().deprecated_io_node) {
+	if (audio_diskstream()->deprecated_io_node) {
 
 		if (!connecting_legal) {
 			ConnectingLegal.connect (mem_fun (*this, &AudioTrack::deprecated_use_diskstream_connections));
@@ -158,33 +155,33 @@ AudioTrack::set_diskstream (AudioDiskstream& ds, void *src)
 int 
 AudioTrack::use_diskstream (string name)
 {
-	AudioDiskstream *dstream;
+	boost::shared_ptr<AudioDiskstream> dstream;
 
-	if ((dstream = dynamic_cast<AudioDiskstream*>(_session.diskstream_by_name (name))) == 0) {
-	  error << string_compose(_("AudioTrack: audio diskstream \"%1\" not known by session"), name) << endmsg;
+	if ((dstream = boost::dynamic_pointer_cast<AudioDiskstream>(_session.diskstream_by_name (name))) == 0) {
+		error << string_compose(_("AudioTrack: audio diskstream \"%1\" not known by session"), name) << endmsg;
 		return -1;
 	}
 	
-	return set_diskstream (*dstream, this);
+	return set_diskstream (dstream, this);
 }
 
 int 
 AudioTrack::use_diskstream (const PBD::ID& id)
 {
-	AudioDiskstream *dstream;
+	boost::shared_ptr<AudioDiskstream> dstream;
 
-	if ((dstream = dynamic_cast<AudioDiskstream*>(_session.diskstream_by_id (id))) == 0) {
+	if ((dstream = boost::dynamic_pointer_cast<AudioDiskstream> (_session.diskstream_by_id (id))) == 0) {
 	  	error << string_compose(_("AudioTrack: audio diskstream \"%1\" not known by session"), id) << endmsg;
 		return -1;
 	}
 	
-	return set_diskstream (*dstream, this);
+	return set_diskstream (dstream, this);
 }
 
-AudioDiskstream&
+boost::shared_ptr<AudioDiskstream>
 AudioTrack::audio_diskstream() const
 {
-	return *dynamic_cast<AudioDiskstream*>(_diskstream);
+	return boost::dynamic_pointer_cast<AudioDiskstream>(_diskstream);
 }
 
 int
@@ -427,7 +424,7 @@ AudioTrack::no_roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nf
 		return 0;
 	}
 
-	audio_diskstream().check_record_status (start_frame, nframes, can_record);
+	audio_diskstream()->check_record_status (start_frame, nframes, can_record);
 
 	bool send_silence;
 	
@@ -494,7 +491,7 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 	Sample* b;
 	Sample* tmpb;
 	jack_nframes_t transport_frame;
-	AudioDiskstream& diskstream = audio_diskstream();
+	boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 	
 	{
 		Glib::RWLock::ReaderLock lm (redirect_lock, Glib::TRY_LOCK);
@@ -521,13 +518,13 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 		   playback distance to zero, thus causing diskstream::commit
 		   to do nothing.
 		*/
-		return diskstream.process (transport_frame, 0, 0, can_record, rec_monitors_input);
+		return diskstream->process (transport_frame, 0, 0, can_record, rec_monitors_input);
 	} 
 
 	_silent = false;
 	apply_gain_automation = false;
 
-	if ((dret = diskstream.process (transport_frame, nframes, offset, can_record, rec_monitors_input)) != 0) {
+	if ((dret = diskstream->process (transport_frame, nframes, offset, can_record, rec_monitors_input)) != 0) {
 		
 		silence (nframes, offset);
 
@@ -540,7 +537,7 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 		just_meter_input (start_frame, end_frame, nframes, offset);
 	}
 
-	if (diskstream.record_enabled() && !can_record && !_session.get_auto_input()) {
+	if (diskstream->record_enabled() && !can_record && !_session.get_auto_input()) {
 
 		/* not actually recording, but we want to hear the input material anyway,
 		   at least potentially (depending on monitoring options)
@@ -548,7 +545,7 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 
 		passthru (start_frame, end_frame, nframes, offset, 0, true);
 
-	} else if ((b = diskstream.playback_buffer(0)) != 0) {
+	} else if ((b = diskstream->playback_buffer(0)) != 0) {
 
 		/*
 		  XXX is it true that the earlier test on n_outputs()
@@ -569,8 +566,8 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 
 		for (i = 0, n = 1; i < limit; ++i, ++n) {
 			memcpy (bufs.get_audio(i).data(nframes), b, sizeof (Sample) * nframes); 
-			if (n < diskstream.n_channels().get(DataType::AUDIO)) {
-				tmpb = diskstream.playback_buffer(n);
+			if (n < diskstream->n_channels().get(DataType::AUDIO)) {
+				tmpb = diskstream->playback_buffer(n);
 				if (tmpb!=0) {
 					b = tmpb;
 				}
@@ -579,7 +576,7 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 
 		/* don't waste time with automation if we're recording or we've just stopped (yes it can happen) */
 
-		if (!diskstream.record_enabled() && _session.transport_rolling()) {
+		if (!diskstream->record_enabled() && _session.transport_rolling()) {
 			Glib::Mutex::Lock am (automation_lock, Glib::TRY_LOCK);
 			
 			if (am.locked() && gain_automation_playback()) {
@@ -615,7 +612,7 @@ AudioTrack::silent_roll (jack_nframes_t nframes, jack_nframes_t start_frame, jac
 
 	silence (nframes, offset);
 
-	return audio_diskstream().process (_session.transport_frame() + offset, nframes, offset, can_record, rec_monitors_input);
+	return audio_diskstream()->process (_session.transport_frame() + offset, nframes, offset, can_record, rec_monitors_input);
 }
 
 int
@@ -627,12 +624,12 @@ AudioTrack::export_stuff (BufferSet& buffers, jack_nframes_t start, jack_nframes
 	RedirectList::iterator i;
 	bool post_fader_work = false;
 	gain_t this_gain = _gain;
-	AudioDiskstream& diskstream = audio_diskstream();
+	boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 	
 	Glib::RWLock::ReaderLock rlock (redirect_lock);
 
 	// FIXME
-	AudioPlaylist* const apl = dynamic_cast<AudioPlaylist*>(diskstream.playlist());
+	AudioPlaylist* const apl = dynamic_cast<AudioPlaylist*>(diskstream->playlist());
 	assert(apl);
 
 	if (apl->read (buffers.get_audio(nframes).data(nframes),
@@ -646,7 +643,7 @@ AudioTrack::export_stuff (BufferSet& buffers, jack_nframes_t start, jack_nframes
 	BufferSet::audio_iterator bi = buffers.audio_begin();
 	++bi;
 	for ( ; bi != buffers.audio_end(); ++bi, ++n) {
-		if (n < diskstream.n_channels().get(DataType::AUDIO)) {
+		if (n < diskstream->n_channels().get(DataType::AUDIO)) {
 			if (apl->read (bi->data(nframes), mix_buffer, gain_buffer, start, nframes, n) != nframes) {
 				return -1;
 			}
@@ -743,9 +740,9 @@ AudioTrack::freeze (InterThreadInfo& itt)
 	string dir;
 	AudioRegion* region;
 	string region_name;
-	AudioDiskstream& diskstream = audio_diskstream();
+	boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 	
-	if ((_freeze_record.playlist = dynamic_cast<AudioPlaylist*>(diskstream.playlist())) == 0) {
+	if ((_freeze_record.playlist = dynamic_cast<AudioPlaylist*>(diskstream->playlist())) == 0) {
 		return;
 	}
 
@@ -813,13 +810,13 @@ AudioTrack::freeze (InterThreadInfo& itt)
 				  (AudioRegion::Flag) (AudioRegion::WholeFile|AudioRegion::DefaultFlags),
 				  false);
 
-	new_playlist->set_orig_diskstream_id (diskstream.id());
+	new_playlist->set_orig_diskstream_id (diskstream->id());
 	new_playlist->add_region (*region, 0);
 	new_playlist->set_frozen (true);
 	region->set_locked (true);
 
-	diskstream.use_playlist (dynamic_cast<AudioPlaylist*>(new_playlist));
-	diskstream.set_record_enabled (false);
+	diskstream->use_playlist (dynamic_cast<AudioPlaylist*>(new_playlist));
+	diskstream->set_record_enabled (false);
 
 	_freeze_record.state = Frozen;
 	FreezeChange(); /* EMIT SIGNAL */
@@ -829,7 +826,7 @@ void
 AudioTrack::unfreeze ()
 {
 	if (_freeze_record.playlist) {
-		audio_diskstream().use_playlist (_freeze_record.playlist);
+		audio_diskstream()->use_playlist (_freeze_record.playlist);
 
 		if (_freeze_record.have_mementos) {
 
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index d00b83f53d..15ad6e442c 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -24,6 +24,7 @@
 
 #include <glibmm/timer.h>
 #include <pbd/pthread_utils.h>
+#include <pbd/unknown_type.h>
 
 #include <ardour/audioengine.h>
 #include <ardour/buffer.h>
@@ -46,6 +47,7 @@ using namespace ARDOUR;
 using namespace PBD;
 
 AudioEngine::AudioEngine (string client_name) 
+	: ports (new Ports)
 {
 	session = 0;
 	session_remove_pending = false;
@@ -257,8 +259,10 @@ AudioEngine::process_callback (jack_nframes_t nframes)
 		return 0;
 	}
 
+	boost::shared_ptr<Ports> p = ports.reader();
+
 	// Prepare ports (ie read data if necessary)
-	for (Ports::iterator i = ports.begin(); i != ports.end(); ++i)
+	for (Ports::iterator i = p->begin(); i != p->end(); ++i)
 		(*i)->cycle_start(nframes);
 	
 	session->process (nframes);
@@ -273,11 +277,14 @@ AudioEngine::process_callback (jack_nframes_t nframes)
 	}
 	
 	// Finalize ports (ie write data if necessary)
-	for (Ports::iterator i = ports.begin(); i != ports.end(); ++i)
+	for (Ports::iterator i = p->begin(); i != p->end(); ++i)
 		(*i)->cycle_end();
 
 	if (last_monitor_check + monitor_check_interval < next_processed_frames) {
-		for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+
+		boost::shared_ptr<Ports> p = ports.reader();
+
+		for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
 			
 			Port *port = (*i);
 			bool x;
@@ -336,7 +343,9 @@ AudioEngine::jack_bufsize_callback (jack_nframes_t nframes)
 	_usecs_per_cycle = (int) floor ((((double) nframes / frame_rate())) * 1000000.0);
 	last_monitor_check = 0;
 
-	for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+	boost::shared_ptr<Ports> p = ports.reader();
+
+	for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
 		(*i)->reset();
 	}
 
@@ -407,21 +416,26 @@ AudioEngine::register_input_port (DataType type, const string& portname)
 		}
 	}
 
-	jack_port_t *p = jack_port_register (_jack, portname.c_str(),
-		type.to_jack_type(), JackPortIsInput, 0);
+	jack_port_t *p = jack_port_register (_jack, portname.c_str(), type.to_jack_type(), JackPortIsInput, 0);
 
 	if (p) {
 
 		Port* newport = 0;
-
+		
 		if (type == DataType::AUDIO)
 			newport = new AudioPort (p);
 		else if (type == DataType::MIDI)
 			newport = new MidiPort (p);
+		else
+			throw unknown_type();
+
+		if (newport != 0) {
+			RCUWriter<Ports> writer (ports);
+			boost::shared_ptr<Ports> ps = writer.get_copy ();
+			ps->insert (ps->begin(), newport);
+			/* writer goes out of scope, forces update */
+		}
 
-		if (newport)
-			ports.insert (ports.begin(), newport);
-		
 		return newport;
 
 	} else {
@@ -449,16 +463,23 @@ AudioEngine::register_output_port (DataType type, const string& portname)
 	
 	if ((p = jack_port_register (_jack, portname.c_str(),
 			type.to_jack_type(), JackPortIsOutput, 0)) != 0) {
-		Port *newport = NULL;
+		
+		Port* newport = 0;
 		
 		if (type == DataType::AUDIO)
 			newport = new AudioPort (p);
 		else if (type == DataType::MIDI)
 			newport = new MidiPort (p);
-
-		if (newport)
-			ports.insert (ports.begin(), newport);
-
+		else
+			throw unknown_type ();
+
+		if (newport != 0) {
+			RCUWriter<Ports> writer (ports);
+			boost::shared_ptr<Ports> ps = writer.get_copy ();
+			ps->insert (ps->begin(), newport);
+			/* writer goes out of scope, forces update */
+		}
+		
 		return newport;
 		
 	} else {
@@ -485,18 +506,25 @@ AudioEngine::unregister_port (Port& port)
 
 	if (ret == 0) {
 
-		for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
-			if (*i == &port) {
-				ports.erase (i);
-				break;
+		{
+
+			RCUWriter<Ports> writer (ports);
+			boost::shared_ptr<Ports> ps = writer.get_copy ();
+
+			for (Ports::iterator i = ps->begin(); i != ps->end(); ++i) {
+				if ((*i) == &port) {
+					ps->erase (i);
+					break;
+				}
 			}
+
+			/* writer goes out of scope, forces update */
 		}
 
 		remove_connections_for (port);
 	}
 
 	return ret;
-
 }
 
 int 
@@ -630,7 +658,9 @@ AudioEngine::get_port_by_name (const string& portname, bool keep)
 		}
 	}
 	
-	for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+	boost::shared_ptr<Ports> pr = ports.reader();
+	
+	for (Ports::iterator i = pr->begin(); i != pr->end(); ++i) {
 		if (portname == (*i)->name()) {
 			return (*i);
 		}
@@ -709,6 +739,50 @@ AudioEngine::n_physical_inputs () const
 	return i;
 }
 
+void
+AudioEngine::get_physical_inputs (vector<string>& ins)
+{
+	const char ** ports;
+	uint32_t i = 0;
+	
+	if (!_jack) {
+		return;
+	}
+	
+	if ((ports = jack_get_ports (_jack, NULL, NULL, JackPortIsPhysical|JackPortIsOutput)) == 0) {
+		return;
+	}
+
+	if (ports) {
+		for (i = 0; ports[i]; ++i) {
+			ins.push_back (ports[i]);
+		}
+		free (ports);
+	}
+}
+
+void
+AudioEngine::get_physical_outputs (vector<string>& outs)
+{
+	const char ** ports;
+	uint32_t i = 0;
+	
+	if (!_jack) {
+		return;
+	}
+	
+	if ((ports = jack_get_ports (_jack, NULL, NULL, JackPortIsPhysical|JackPortIsInput)) == 0) {
+		return;
+	}
+
+	if (ports) {
+		for (i = 0; ports[i]; ++i) {
+			outs.push_back (ports[i]);
+		}
+		free (ports);
+	}
+}
+
 string
 AudioEngine::get_nth_physical (DataType type, uint32_t n, int flag)
 {
@@ -836,12 +910,19 @@ AudioEngine::remove_all_ports ()
 	/* process lock MUST be held */
 
 	if (_jack) {
-		for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+		boost::shared_ptr<Ports> p = ports.reader();
+
+		for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
 			jack_port_unregister (_jack, (*i)->_port);
 		}
 	}
 
-	ports.clear ();
+	{
+		RCUWriter<Ports> writer (ports);
+		boost::shared_ptr<Ports> ps = writer.get_copy ();
+		ps->clear ();
+	}
+
 	port_connections.clear ();
 }
 
@@ -941,7 +1022,7 @@ AudioEngine::reconnect_to_jack ()
 	if (_jack) {
 		disconnect_from_jack ();
 		/* XXX give jackd a chance */
-        Glib::usleep (250000);
+		Glib::usleep (250000);
 	}
 
 	if (connect_to_jack (jack_client_name)) {
@@ -951,7 +1032,9 @@ AudioEngine::reconnect_to_jack ()
 
 	Ports::iterator i;
 
-	for (i = ports.begin(); i != ports.end(); ++i) {
+	boost::shared_ptr<Ports> p = ports.reader ();
+
+	for (i = p->begin(); i != p->end(); ++i) {
 
 		/* XXX hack hack hack */
 
@@ -973,8 +1056,9 @@ AudioEngine::reconnect_to_jack ()
 		}
 	}
 
-	if (i != ports.end()) {
-		for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+	if (i != p->end()) {
+		/* failed */
+		for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
 			jack_port_unregister (_jack, (*i)->_port);
 		}
 		return -1;
diff --git a/libs/ardour/auditioner.cc b/libs/ardour/auditioner.cc
index af3072d215..3109323acd 100644
--- a/libs/ardour/auditioner.cc
+++ b/libs/ardour/auditioner.cc
@@ -49,7 +49,7 @@ Auditioner::Auditioner (Session& s)
 	}
 
 	if (right.length()) {
-		audio_diskstream().add_channel();
+		audio_diskstream()->add_channel();
 		add_output_port (right, this, DataType::AUDIO);
 	}
 
@@ -119,11 +119,11 @@ Auditioner::audition_region (AudioRegion& region)
 	_diskstream->playlist()->add_region (*the_region, 0, 1, false);
 
 	while (_diskstream->n_channels().get(DataType::AUDIO) < the_region->n_channels()) {
-		audio_diskstream().add_channel ();
+		audio_diskstream()->add_channel ();
 	}
 
 	while (_diskstream->n_channels().get(DataType::AUDIO) > the_region->n_channels()) {
-		audio_diskstream().remove_channel ();
+		audio_diskstream()->remove_channel ();
 	}
 
 	/* force a panner reset now that we have all channels */
diff --git a/libs/ardour/automation_event.cc b/libs/ardour/automation_event.cc
index dc1767d1e7..ccfcef28f4 100644
--- a/libs/ardour/automation_event.cc
+++ b/libs/ardour/automation_event.cc
@@ -33,6 +33,8 @@ using namespace ARDOUR;
 using namespace sigc;
 using namespace PBD;
 
+sigc::signal<void,AutomationList *> AutomationList::AutomationListCreated;
+
 #if 0
 static void dumpit (const AutomationList& al, string prefix = "")
 {
@@ -64,6 +66,8 @@ AutomationList::AutomationList (double defval, bool with_state)
 	if (!no_state) {
 		save_state (_("initial"));
 	}
+
+        AutomationListCreated(this);
 }
 
 AutomationList::AutomationList (const AutomationList& other)
@@ -91,6 +95,7 @@ AutomationList::AutomationList (const AutomationList& other)
 	}
 
 	mark_dirty ();
+        AutomationListCreated(this);
 }
 
 AutomationList::AutomationList (const AutomationList& other, double start, double end)
@@ -123,6 +128,7 @@ AutomationList::AutomationList (const AutomationList& other, double start, doubl
 	delete section;
 
 	mark_dirty ();
+        AutomationListCreated(this);
 }
 
 AutomationList::~AutomationList()
diff --git a/libs/ardour/curve.cc b/libs/ardour/curve.cc
index b0052c96fb..7d62c5bc94 100644
--- a/libs/ardour/curve.cc
+++ b/libs/ardour/curve.cc
@@ -40,11 +40,14 @@ using namespace ARDOUR;
 using namespace sigc;
 using namespace PBD;
 
+sigc::signal<void, Curve*> Curve::CurveCreated;
+
 Curve::Curve (double minv, double maxv, double canv, bool nostate)
 	: AutomationList (canv, nostate)
 {
 	min_yval = minv;
 	max_yval = maxv;
+        CurveCreated(this);
 }
 
 Curve::Curve (const Curve& other)
@@ -52,6 +55,7 @@ Curve::Curve (const Curve& other)
 {
 	min_yval = other.min_yval;
 	max_yval = other.max_yval;
+        CurveCreated(this);
 }
 
 Curve::Curve (const Curve& other, double start, double end)
@@ -59,6 +63,7 @@ Curve::Curve (const Curve& other, double start, double end)
 {
 	min_yval = other.min_yval;
 	max_yval = other.max_yval;
+        CurveCreated(this);
 }
 
 Curve::~Curve ()
diff --git a/libs/ardour/diskstream.cc b/libs/ardour/diskstream.cc
index 22a0b0460e..9a80f3e70f 100644
--- a/libs/ardour/diskstream.cc
+++ b/libs/ardour/diskstream.cc
@@ -63,7 +63,6 @@ using namespace PBD;
  */
 jack_nframes_t Diskstream::disk_io_chunk_frames = 1024 * 256;
 
-sigc::signal<void,Diskstream*>    Diskstream::DiskstreamCreated;
 sigc::signal<void,list<Source*>*> Diskstream::DeleteSources;
 sigc::signal<void>                Diskstream::DiskOverrun;
 sigc::signal<void>                Diskstream::DiskUnderrun;
@@ -86,7 +85,6 @@ Diskstream::Diskstream (Session& sess, const XMLNode& node)
 void
 Diskstream::init (Flag f)
 {
-	_refcnt = 0;
 	_flags = f;
 	_io = 0;
 	_alignment_style = ExistingMaterial;
diff --git a/libs/ardour/location.cc b/libs/ardour/location.cc
index 5b5f733138..ca88a2851b 100644
--- a/libs/ardour/location.cc
+++ b/libs/ardour/location.cc
@@ -834,3 +834,14 @@ Locations::num_range_markers () const
 	}
 	return cnt;
 }
+
+Location *
+Locations::get_location_by_id(PBD::ID id)
+{
+    LocationList::iterator it;
+    for (it  = locations.begin(); it != locations.end(); it++)
+        if (id == (*it)->id())
+            return *it;
+
+    return 0;
+}
diff --git a/libs/ardour/midi_diskstream.cc b/libs/ardour/midi_diskstream.cc
index 40b0b11564..e42e455df0 100644
--- a/libs/ardour/midi_diskstream.cc
+++ b/libs/ardour/midi_diskstream.cc
@@ -80,7 +80,6 @@ MidiDiskstream::MidiDiskstream (Session &sess, const string &name, Diskstream::F
 	in_set_state = false;
 
 	assert(!destructive());
-	DiskstreamCreated (this); /* EMIT SIGNAL */
 }
 	
 MidiDiskstream::MidiDiskstream (Session& sess, const XMLNode& node)
@@ -109,8 +108,6 @@ MidiDiskstream::MidiDiskstream (Session& sess, const XMLNode& node)
 	if (destructive()) {
 		use_destructive_playlist ();
 	}
-
-	DiskstreamCreated (this); /* EMIT SIGNAL */
 }
 
 void
@@ -1108,7 +1105,7 @@ MidiDiskstream::transport_stopped (struct tm& when, time_t twhen, bool abort_cap
 
 		_playlist->thaw ();
 		XMLNode &after = _playlist->get_state();
-		_session.add_command (new MementoCommand<Playlist>(*_playlist, before, after));
+		_session.add_command (new MementoCommand<Playlist>(*_playlist, &before, &after));
 
 		mark_write_completed = true;
 
@@ -1526,9 +1523,9 @@ MidiDiskstream::get_playback(MidiBuffer& dst, jack_nframes_t start, jack_nframes
 	for (size_t i=0; i < dst.size(); ++i) {
 		assert(dst[i].time >= start);
 		assert(dst[i].time <= end);
-		cerr << "Translating event stamp " << dst[i].time << " to ";
+		//cerr << "Translating event stamp " << dst[i].time << " to ";
 		dst[i].time -= start;
-		cerr << dst[i].time << endl;
+		//cerr << dst[i].time << endl;
 
 	}
 }
diff --git a/libs/ardour/midi_track.cc b/libs/ardour/midi_track.cc
index 91aad5ea80..aeff92bed3 100644
--- a/libs/ardour/midi_track.cc
+++ b/libs/ardour/midi_track.cc
@@ -51,18 +51,17 @@ MidiTrack::MidiTrack (Session& sess, string name, Route::Flag flag, TrackMode mo
 		dflags = MidiDiskstream::Flag (dflags | MidiDiskstream::Recordable);
 	}
 
-	if (mode == Destructive) {
-		dflags = MidiDiskstream::Flag (dflags | MidiDiskstream::Destructive);
-	}
+	assert(mode != Destructive);
+
+	boost::shared_ptr<MidiDiskstream> ds (new MidiDiskstream (_session, name, dflags));
+	_session.add_diskstream (ds);
 
-	MidiDiskstream* ds = new MidiDiskstream (_session, name, dflags);
+	set_diskstream (boost::dynamic_pointer_cast<MidiDiskstream> (ds));
 	
 	_declickable = true;
 	_freeze_record.state = NoFreeze;
 	_saved_meter_point = _meter_point;
 	_mode = mode;
-
-	set_diskstream (*ds);
 }
 
 MidiTrack::MidiTrack (Session& sess, const XMLNode& node)
@@ -76,20 +75,13 @@ MidiTrack::MidiTrack (Session& sess, const XMLNode& node)
 
 MidiTrack::~MidiTrack ()
 {
-	if (_diskstream) {
-		_diskstream->unref();
-	}
 }
 
 
 int
-MidiTrack::set_diskstream (MidiDiskstream& ds)
+MidiTrack::set_diskstream (boost::shared_ptr<MidiDiskstream> ds)
 {
-	if (_diskstream) {
-		_diskstream->unref();
-	}
-
-	_diskstream = &ds.ref();
+	_diskstream = ds;
 	_diskstream->set_io (*this);
 	_diskstream->set_destructive (_mode == Destructive);
 
@@ -107,33 +99,33 @@ MidiTrack::set_diskstream (MidiDiskstream& ds)
 int 
 MidiTrack::use_diskstream (string name)
 {
-	MidiDiskstream *dstream;
+	boost::shared_ptr<MidiDiskstream> dstream;
 
-	if ((dstream = dynamic_cast<MidiDiskstream*>(_session.diskstream_by_name (name))) == 0) {
-	  error << string_compose(_("MidiTrack: midi diskstream \"%1\" not known by session"), name) << endmsg;
+	if ((dstream = boost::dynamic_pointer_cast<MidiDiskstream>(_session.diskstream_by_name (name))) == 0) {
+		error << string_compose(_("MidiTrack: midi diskstream \"%1\" not known by session"), name) << endmsg;
 		return -1;
 	}
 	
-	return set_diskstream (*dstream);
+	return set_diskstream (dstream);
 }
 
 int 
 MidiTrack::use_diskstream (const PBD::ID& id)
 {
-	MidiDiskstream *dstream;
+	boost::shared_ptr<MidiDiskstream> dstream;
 
-	if ((dstream = dynamic_cast<MidiDiskstream*>(_session.diskstream_by_id (id))) == 0) {
+	if ((dstream = boost::dynamic_pointer_cast<MidiDiskstream> (_session.diskstream_by_id (id))) == 0) {
 	  	error << string_compose(_("MidiTrack: midi diskstream \"%1\" not known by session"), id) << endmsg;
 		return -1;
 	}
 	
-	return set_diskstream (*dstream);
+	return set_diskstream (dstream);
 }
 
-MidiDiskstream&
+boost::shared_ptr<MidiDiskstream>
 MidiTrack::midi_diskstream() const
 {
-	return *dynamic_cast<MidiDiskstream*>(_diskstream);
+	return boost::dynamic_pointer_cast<MidiDiskstream>(_diskstream);
 }
 
 int
@@ -377,7 +369,7 @@ MidiTrack::no_roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfr
 		return 0;
 	}
 
-	midi_diskstream().check_record_status (start_frame, nframes, can_record);
+	midi_diskstream()->check_record_status (start_frame, nframes, can_record);
 
 	bool send_silence;
 	
@@ -441,7 +433,7 @@ MidiTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nframe
 		  bool can_record, bool rec_monitors_input)
 {
 	int dret;
-	MidiDiskstream& diskstream = midi_diskstream();
+	boost::shared_ptr<MidiDiskstream> diskstream = midi_diskstream();
 
 	{
 		Glib::RWLock::ReaderLock lm (redirect_lock, Glib::TRY_LOCK);
@@ -468,12 +460,12 @@ MidiTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nframe
 		   playback distance to zero, thus causing diskstream::commit
 		   to do nothing.
 		   */
-		return diskstream.process (transport_frame, 0, 0, can_record, rec_monitors_input);
+		return diskstream->process (transport_frame, 0, 0, can_record, rec_monitors_input);
 	} 
 
 	_silent = false;
 
-	if ((dret = diskstream.process (transport_frame, nframes, offset, can_record, rec_monitors_input)) != 0) {
+	if ((dret = diskstream->process (transport_frame, nframes, offset, can_record, rec_monitors_input)) != 0) {
 
 		silence (nframes, offset);
 
@@ -486,7 +478,7 @@ MidiTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nframe
 		just_meter_input (start_frame, end_frame, nframes, offset);
 	}
 
-	if (diskstream.record_enabled() && !can_record && !_session.get_auto_input()) {
+	if (diskstream->record_enabled() && !can_record && !_session.get_auto_input()) {
 
 		/* not actually recording, but we want to hear the input material anyway,
 		   at least potentially (depending on monitoring options)
@@ -509,7 +501,7 @@ MidiTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nframe
 		//const size_t limit = n_process_buffers().get(DataType::AUDIO);
 		BufferSet& bufs = _session.get_scratch_buffers (n_process_buffers());
 
-		diskstream.get_playback(bufs.get_midi(0), start_frame, end_frame);
+		diskstream->get_playback(bufs.get_midi(0), start_frame, end_frame);
 
 		process_output_buffers (bufs, start_frame, end_frame, nframes, offset,
 				(!_session.get_record_enabled() || !_session.get_do_not_record_plugins()), declick, (_meter_point != MeterInput));
@@ -537,7 +529,7 @@ MidiTrack::silent_roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack
 
 	silence (nframes, offset);
 
-	return midi_diskstream().process (_session.transport_frame() + offset, nframes, offset, can_record, rec_monitors_input);
+	return midi_diskstream()->process (_session.transport_frame() + offset, nframes, offset, can_record, rec_monitors_input);
 }
 
 void
diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index 2ea6c314c1..039f88e2ea 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -114,7 +114,6 @@ Route::init ()
 
 Route::~Route ()
 {
-	GoingAway (); /* EMIT SIGNAL */
 	clear_redirects (this);
 
 	if (_control_outs) {
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index ab8d867414..7d5f838499 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -266,6 +266,7 @@ Session::Session (AudioEngine &eng,
 	  pending_events (2048),
 	  //midi_requests (128), // the size of this should match the midi request pool size
 	  _send_smpte_update (false),
+	  diskstreams (new DiskstreamList),
 	  routes (new RouteList),
 	  auditioner ((Auditioner*) 0),
 	  _click_io ((IO*) 0),
@@ -273,7 +274,7 @@ Session::Session (AudioEngine &eng,
 {
 	bool new_session;
 
-	cerr << "Loading session " << fullpath << " using snapshot " << snapshot_name << endl;
+	cerr << "Loading session " << fullpath << " using snapshot " << snapshot_name << " (1)" << endl;
 
 	n_physical_outputs = _engine.n_physical_outputs();
 	n_physical_inputs =  _engine.n_physical_inputs();
@@ -320,13 +321,14 @@ Session::Session (AudioEngine &eng,
 	  pending_events (2048),
 	  //midi_requests (16),
 	  _send_smpte_update (false),
+	  diskstreams (new DiskstreamList),
 	  routes (new RouteList),
 	  main_outs (0)
 
 {
 	bool new_session;
 
-	cerr << "Loading session " << fullpath << " using snapshot " << snapshot_name << endl;
+	cerr << "Loading session " << fullpath << " using snapshot " << snapshot_name << " (2)" << endl;
 
 	n_physical_outputs = max (requested_physical_out, _engine.n_physical_outputs());
 	n_physical_inputs = max (requested_physical_in, _engine.n_physical_inputs());
@@ -339,13 +341,17 @@ Session::Session (AudioEngine &eng,
 
 	if (control_out_channels) {
 		shared_ptr<Route> r (new Route (*this, _("monitor"), -1, control_out_channels, -1, control_out_channels, Route::ControlOut));
-		add_route (r);
+		RouteList rl;
+		rl.push_back (r);
+		add_routes (rl);
 		_control_out = r;
 	}
 
 	if (master_out_channels) {
 		shared_ptr<Route> r (new Route (*this, _("master"), -1, master_out_channels, -1, master_out_channels, Route::MasterOut));
-		add_route (r);
+		RouteList rl;
+		rl.push_back (r);
+		add_routes (rl);
 		_master_out = r;
 	} else {
 		/* prohibit auto-connect to master, because there isn't one */
@@ -445,18 +451,43 @@ Session::~Session ()
 	}
 	
 #ifdef TRACK_DESTRUCTION
-	cerr << "delete diskstreams\n";
+	cerr << "delete routes\n";
 #endif /* TRACK_DESTRUCTION */
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ) {
-		DiskstreamList::iterator tmp;
-
-		tmp = i;
-		++tmp;
+        {
+		RCUWriter<RouteList> writer (routes);
+		boost::shared_ptr<RouteList> r = writer.get_copy ();
+		for (RouteList::iterator i = r->begin(); i != r->end(); ) {
+			RouteList::iterator tmp;
+			tmp = i;
+			++tmp;
+			(*i)->drop_references ();
+			i = tmp;
+		}
+		r->clear ();
+		/* writer goes out of scope and updates master */
+	}
 
-		delete *i;
+	routes.flush ();
 
-		i = tmp;
-	}
+#ifdef TRACK_DESTRUCTION
+	cerr << "delete diskstreams\n";
+#endif /* TRACK_DESTRUCTION */
+       {
+	       RCUWriter<DiskstreamList> dwriter (diskstreams);
+	       boost::shared_ptr<DiskstreamList> dsl = dwriter.get_copy();
+	       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ) {
+		       DiskstreamList::iterator tmp;
+		       
+		       tmp = i;
+		       ++tmp;
+		       
+		       (*i)->drop_references ();
+		       
+		       i = tmp;
+	       }
+	       dsl->clear ();
+       }
+       diskstreams.flush ();
 
 #ifdef TRACK_DESTRUCTION
 	cerr << "delete audio sources\n";
@@ -867,7 +898,7 @@ Session::playlist_length_changed (Playlist* pl)
 }
 
 void
-Session::diskstream_playlist_changed (Diskstream* dstream)
+Session::diskstream_playlist_changed (boost::shared_ptr<Diskstream> dstream)
 {
 	Playlist *playlist;
 
@@ -941,13 +972,10 @@ Session::set_auto_input (bool yn)
 		
 		if (Config->get_use_hardware_monitoring() && transport_rolling()) {
 			/* auto-input only makes a difference if we're rolling */
+			
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-			/* Even though this can called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					//cerr << "switching to input = " << !auto_input << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (!auto_input);   
@@ -964,16 +992,19 @@ void
 Session::reset_input_monitor_state ()
 {
 	if (transport_rolling()) {
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if ((*i)->record_enabled ()) {
 				//cerr << "switching to input = " << !auto_input << __FILE__ << __LINE__ << endl << endl;
 				(*i)->monitor_input (Config->get_use_hardware_monitoring() && !auto_input);
 			}
 		}
 	} else {
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if ((*i)->record_enabled ()) {
 				//cerr << "switching to input = " << !auto_input << __FILE__ << __LINE__ << endl << endl;
 				(*i)->monitor_input (Config->get_use_hardware_monitoring());
@@ -1015,7 +1046,6 @@ Session::auto_punch_start_changed (Location* location)
 	if (get_record_enabled() && get_punch_in()) {
 		/* capture start has been changed, so save new pending state */
 		save_state ("", true);
-                save_history("");
 	}
 }	
 
@@ -1246,13 +1276,8 @@ Session::enable_record ()
 		deliver_mmc(MIDI::MachineControl::cmdRecordStrobe, _last_record_location);
 
 		if (Config->get_use_hardware_monitoring() && auto_input) {
-			/* Even though this can be called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					(*i)->monitor_input (true);   
 				}
@@ -1285,13 +1310,9 @@ Session::disable_record (bool rt_context, bool force)
 			deliver_mmc (MIDI::MachineControl::cmdRecordExit, _transport_frame);
 
 		if (Config->get_use_hardware_monitoring() && auto_input) {
-			/* Even though this can be called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 			
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					(*i)->monitor_input (false);   
 				}
@@ -1312,13 +1333,9 @@ Session::step_back_from_record ()
 	g_atomic_int_set (&_record_status, Enabled);
 
 	if (Config->get_use_hardware_monitoring()) {
-		/* Even though this can be called from RT context we are using
-		   a non-tentative rwlock here,  because the action must occur.
-		   The rarity and short potential lock duration makes this "OK"
-		*/
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 		
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		        if (auto_input && (*i)->record_enabled ()) {
 			        //cerr << "switching from input" << __FILE__ << __LINE__ << endl << endl;
 		                (*i)->monitor_input (false);   
@@ -1337,7 +1354,6 @@ Session::maybe_enable_record ()
 	*/
 
 	save_state ("", true);
-        save_history ("");
 
 	if (_transport_speed) {
 		if (!punch_in) {
@@ -1442,7 +1458,6 @@ Session::set_block_size (jack_nframes_t nframes)
 	*/
 
 	{ 
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
 			
 		current_block_size = nframes;
 		
@@ -1461,7 +1476,8 @@ Session::set_block_size (jack_nframes_t nframes)
 			(*i)->set_block_size (nframes);
 		}
 		
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			(*i)->set_block_size (nframes);
 		}
 
@@ -1641,7 +1657,88 @@ Session::resort_routes_using (shared_ptr<RouteList> r)
 	
 }
 
-boost::shared_ptr<MidiTrack>
+list<boost::shared_ptr<MidiTrack> >
+Session::new_midi_track (TrackMode mode, uint32_t how_many)
+{
+	char track_name[32];
+	uint32_t track_id = 0;
+	uint32_t n = 0;
+	uint32_t channels_used = 0;
+	string port;
+	RouteList new_routes;
+	list<boost::shared_ptr<MidiTrack> > ret;
+
+	/* count existing audio tracks */
+
+	{
+		shared_ptr<RouteList> r = routes.reader ();
+
+		for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+			if (dynamic_cast<MidiTrack*>((*i).get()) != 0) {
+				if (!(*i)->hidden()) {
+					n++;
+					channels_used += (*i)->n_inputs().get(DataType::MIDI);
+				}
+			}
+		}
+	}
+
+	while (how_many) {
+
+		/* check for duplicate route names, since we might have pre-existing
+		   routes with this name (e.g. create Midi1, Midi2, delete Midi1,
+		   save, close,restart,add new route - first named route is now
+		   Midi2)
+		*/
+		
+
+		do {
+			++track_id;
+
+			snprintf (track_name, sizeof(track_name), "Midi %" PRIu32, track_id);
+
+			if (route_by_name (track_name) == 0) {
+				break;
+			}
+			
+		} while (track_id < (UINT_MAX-1));
+
+		try {
+			shared_ptr<MidiTrack> track (new MidiTrack (*this, track_name, Route::Flag (0), mode));
+			
+			if (track->ensure_io (ChanCount(DataType::MIDI, 1), ChanCount(DataType::MIDI, 1), false, this)) {
+				error << "cannot configure 1 in/1 out configuration for new midi track" << endmsg;
+			}
+			
+			channels_used += track->n_inputs ().get(DataType::MIDI);
+
+			track->DiskstreamChanged.connect (mem_fun (this, &Session::resort_routes));
+			track->set_remote_control_id (ntracks());
+
+			new_routes.push_back (track);
+			ret.push_back (track);
+		}
+
+		catch (failed_constructor &err) {
+			error << _("Session: could not create new midi track.") << endmsg;
+			// XXX should we delete the tracks already created? 
+			ret.clear ();
+			return ret;
+		}
+		
+		--how_many;
+	}
+
+	if (!new_routes.empty()) {
+		add_routes (new_routes, false);
+		save_state (_current_snapshot_name);
+	}
+
+	return ret;
+}
+
+#if 0
+std::list<boost::shared_ptr<MidiTrack> >
 Session::new_midi_track (TrackMode mode)
 {
 	char track_name[32];
@@ -1686,50 +1783,7 @@ Session::new_midi_track (TrackMode mode)
 			error << string_compose (_("cannot configure %1 in/%2 out configuration for new midi track"), track_name)
 			      << endmsg;
 		}
-#if 0
-		if (nphysical_in) {
-			for (uint32_t x = 0; x < track->n_inputs() && x < nphysical_in; ++x) {
-				
-				port = "";
-				
-				if (input_auto_connect & AutoConnectPhysical) {
-					port = _engine.get_nth_physical_input ((channels_used+x)%nphysical_in);
-				} 
-				
-				if (port.length() && track->connect_input (track->input (x), port, this)) {
-					break;
-				}
-			}
-		}
-		
-		for (uint32_t x = 0; x < track->n_outputs(); ++x) {
-			
-			port = "";
-
-			if (nphysical_out && (output_auto_connect & AutoConnectPhysical)) {
-				port = _engine.get_nth_physical_output ((channels_used+x)%nphysical_out);
-			} else if (output_auto_connect & AutoConnectMaster) {
-				if (_master_out) {
-					port = _master_out->input (x%_master_out->n_inputs())->name();
-				}
-			}
-
-			if (port.length() && track->connect_output (track->output (x), port, this)) {
-				break;
-			}
-		}
-
-		if (_control_out) {
-			vector<string> cports;
-			uint32_t ni = _control_out->n_inputs();
 
-			for (n = 0; n < ni; ++n) {
-				cports.push_back (_control_out->input(n)->name());
-			}
-
-			track->set_control_outs (cports);
-		}
-#endif
 		track->DiskstreamChanged.connect (mem_fun (this, &Session::resort_routes));
 
 		add_route (track);
@@ -1744,7 +1798,6 @@ Session::new_midi_track (TrackMode mode)
 	}
 }
 
-
 boost::shared_ptr<Route>
 Session::new_midi_route ()
 {
@@ -1832,17 +1885,18 @@ Session::new_midi_route ()
 		return shared_ptr<Route> ((Route*) 0);
 	}
 }
+#endif
 
-
-shared_ptr<AudioTrack>
-Session::new_audio_track (int input_channels, int output_channels, TrackMode mode)
+list<boost::shared_ptr<AudioTrack> >
+Session::new_audio_track (int input_channels, int output_channels, TrackMode mode, uint32_t how_many)
 {
 	char track_name[32];
+	uint32_t track_id = 0;
 	uint32_t n = 0;
 	uint32_t channels_used = 0;
 	string port;
-	uint32_t nphysical_in;
-	uint32_t nphysical_out;
+	RouteList new_routes;
+	list<boost::shared_ptr<AudioTrack> > ret;
 
 	/* count existing audio tracks */
 
@@ -1859,105 +1913,133 @@ Session::new_audio_track (int input_channels, int output_channels, TrackMode mod
 		}
 	}
 
-	/* check for duplicate route names, since we might have pre-existing
-	   routes with this name (e.g. create Audio1, Audio2, delete Audio1,
-	   save, close,restart,add new route - first named route is now
-	   Audio2)
-	*/
+	vector<string> physinputs;
+	vector<string> physoutputs;
+	uint32_t nphysical_in;
+	uint32_t nphysical_out;
 
-	do {
-		snprintf (track_name, sizeof(track_name), "Audio %" PRIu32, n+1);
-		if (route_by_name (track_name) == 0) {
-			break;
-		}
-		n++;
+	_engine.get_physical_outputs (physoutputs);
+	_engine.get_physical_inputs (physinputs);
 
-	} while (n < (UINT_MAX-1));
+	while (how_many) {
 
-	if (input_auto_connect & AutoConnectPhysical) {
-		nphysical_in = n_physical_inputs;
-	} else {
-		nphysical_in = 0;
-	}
+		/* check for duplicate route names, since we might have pre-existing
+		   routes with this name (e.g. create Audio1, Audio2, delete Audio1,
+		   save, close,restart,add new route - first named route is now
+		   Audio2)
+		*/
+		
 
-	if (output_auto_connect & AutoConnectPhysical) {
-		nphysical_out = n_physical_outputs;
-	} else {
-		nphysical_out = 0;
-	}
+		do {
+			++track_id;
 
-	try {
-		shared_ptr<AudioTrack> track (new AudioTrack (*this, track_name, Route::Flag (0), mode));
+			snprintf (track_name, sizeof(track_name), "Audio %" PRIu32, track_id);
 
-		if (track->ensure_io (input_channels, output_channels, false, this)) {
-			error << string_compose (_("cannot configure %1 in/%2 out configuration for new audio track"),
-					  input_channels, output_channels)
-			      << endmsg;
-		}
+			if (route_by_name (track_name) == 0) {
+				break;
+			}
+			
+		} while (track_id < (UINT_MAX-1));
 
-		if (nphysical_in) {
-			for (uint32_t x = 0; x < track->n_inputs().get(DataType::AUDIO) && x < nphysical_in; ++x) {
+		if (input_auto_connect & AutoConnectPhysical) {
+			nphysical_in = min (n_physical_inputs, (uint32_t) physinputs.size());
+		} else {
+			nphysical_in = 0;
+		}
+		
+		if (output_auto_connect & AutoConnectPhysical) {
+			nphysical_out = min (n_physical_outputs, (uint32_t) physinputs.size());
+		} else {
+			nphysical_out = 0;
+		}
+		
+		try {
+			shared_ptr<AudioTrack> track (new AudioTrack (*this, track_name, Route::Flag (0), mode));
+			
+			if (track->ensure_io (input_channels, output_channels, false, this)) {
+				error << string_compose (_("cannot configure %1 in/%2 out configuration for new audio track"),
+							 input_channels, output_channels)
+				      << endmsg;
+			}
+			
+			if (nphysical_in) {
+				for (uint32_t x = 0; x < track->n_inputs().get(DataType::AUDIO) && x < nphysical_in; ++x) {
+					
+					port = "";
+					
+					if (input_auto_connect & AutoConnectPhysical) {
+						port = physinputs[(channels_used+x)%nphysical_in];
+					} 
+					
+					if (port.length() && track->connect_input (track->input (x), port, this)) {
+						break;
+					}
+				}
+			}
+			
+			for (uint32_t x = 0; x < track->n_outputs().get(DataType::MIDI); ++x) {
 				
 				port = "";
 				
-				if (input_auto_connect & AutoConnectPhysical) {
-					port = _engine.get_nth_physical_input (DataType::AUDIO, (channels_used+x)%nphysical_in);
-				} 
+				if (nphysical_out && (output_auto_connect & AutoConnectPhysical)) {
+					port = physoutputs[(channels_used+x)%nphysical_out];
+				} else if (output_auto_connect & AutoConnectMaster) {
+					if (_master_out) {
+						port = _master_out->input (x%_master_out->n_inputs().get(DataType::AUDIO))->name();
+					}
+				}
 				
-				if (port.length() && track->connect_input (track->input (x), port, this)) {
+				if (port.length() && track->connect_output (track->output (x), port, this)) {
 					break;
 				}
 			}
-		}
-		
-		for (uint32_t x = 0; x < track->n_outputs().get(DataType::AUDIO); ++x) {
 			
-			port = "";
+			channels_used += track->n_inputs ().get(DataType::AUDIO);
 
-			if (nphysical_out && (output_auto_connect & AutoConnectPhysical)) {
-				port = _engine.get_nth_physical_output (DataType::AUDIO, (channels_used+x)%nphysical_out);
-			} else if (output_auto_connect & AutoConnectMaster) {
-				if (_master_out) {
-					port = _master_out->audio_input (x%_master_out->n_inputs().get(DataType::AUDIO))->name();
+			if (_control_out) {
+				vector<string> cports;
+				uint32_t ni = _control_out->n_inputs().get(DataType::AUDIO);
+				
+				for (n = 0; n < ni; ++n) {
+					cports.push_back (_control_out->input(n)->name());
 				}
+				
+				track->set_control_outs (cports);
 			}
+			
+			track->DiskstreamChanged.connect (mem_fun (this, &Session::resort_routes));
+			track->set_remote_control_id (ntracks());
 
-			if (port.length() && track->connect_output (track->output (x), port, this)) {
-				break;
-			}
+			new_routes.push_back (track);
+			ret.push_back (track);
 		}
 
-		if (_control_out) {
-			vector<string> cports;
-			uint32_t ni = _control_out->n_inputs().get(DataType::AUDIO);
-
-			for (n = 0; n < ni; ++n) {
-				cports.push_back (_control_out->audio_input(n)->name());
-			}
-
-			track->set_control_outs (cports);
+		catch (failed_constructor &err) {
+			error << _("Session: could not create new audio track.") << endmsg;
+			// XXX should we delete the tracks already created? 
+			ret.clear ();
+			return ret;
 		}
-
-		track->DiskstreamChanged.connect (mem_fun (this, &Session::resort_routes));
-
-		add_route (track);
-
-		track->set_remote_control_id (ntracks());
-		return track;
+		
+		--how_many;
 	}
 
-	catch (failed_constructor &err) {
-		error << _("Session: could not create new audio track.") << endmsg;
-		return shared_ptr<AudioTrack> ((AudioTrack*) 0);
+	if (!new_routes.empty()) {
+		add_routes (new_routes, false);
+		save_state (_current_snapshot_name);
 	}
+
+	return ret;
 }
 
-shared_ptr<Route>
-Session::new_audio_route (int input_channels, int output_channels)
+Session::RouteList
+Session::new_audio_route (int input_channels, int output_channels, uint32_t how_many)
 {
 	char bus_name[32];
+	uint32_t bus_id = 1;
 	uint32_t n = 0;
 	string port;
+	RouteList ret;
 
 	/* count existing audio busses */
 
@@ -1967,127 +2049,148 @@ Session::new_audio_route (int input_channels, int output_channels)
 		for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
 			if (dynamic_cast<AudioTrack*>((*i).get()) == 0) {
 				if (!(*i)->hidden()) {
-					n++;
+					bus_id++;
 				}
 			}
 		}
 	}
 
-	do {
-		snprintf (bus_name, sizeof(bus_name), "Bus %" PRIu32, n+1);
-		if (route_by_name (bus_name) == 0) {
-			break;
-		}
-		n++;
+	vector<string> physinputs;
+	vector<string> physoutputs;
 
-	} while (n < (UINT_MAX-1));
+	_engine.get_physical_outputs (physoutputs);
+	_engine.get_physical_inputs (physinputs);
 
-	try {
-		shared_ptr<Route> bus (new Route (*this, bus_name, -1, -1, -1, -1, Route::Flag(0), DataType::AUDIO));
+	while (how_many) {
 
-		if (bus->ensure_io (input_channels, output_channels, false, this)) {
-			error << string_compose (_("cannot configure %1 in/%2 out configuration for new audio track"),
-					  input_channels, output_channels)
-			      << endmsg;
-		}
+		do {
+			++bus_id;
 
-		for (uint32_t x = 0; x < bus->n_inputs().get(DataType::AUDIO); ++x) {
-			
-			port = "";
+			snprintf (bus_name, sizeof(bus_name), "Bus %" PRIu32, bus_id);
 
-			if (input_auto_connect & AutoConnectPhysical) {
-				port = _engine.get_nth_physical_input (DataType::AUDIO, (n+x)%n_physical_inputs);
-			} 
-			
-			if (port.length() && bus->connect_input (bus->input (x), port, this)) {
+			if (route_by_name (bus_name) == 0) {
 				break;
 			}
-		}
 
-		for (uint32_t x = 0; x < bus->n_outputs().get(DataType::AUDIO); ++x) {
-			
-			port = "";
+		} while (bus_id < (UINT_MAX-1));
 
-			if (output_auto_connect & AutoConnectPhysical) {
-				port = _engine.get_nth_physical_input (DataType::AUDIO, (n+x)%n_physical_outputs);
-			} else if (output_auto_connect & AutoConnectMaster) {
-				if (_master_out) {
-					port = _master_out->audio_input (x%_master_out->n_inputs().get(DataType::AUDIO))->name();
+		try {
+			shared_ptr<Route> bus (new Route (*this, bus_name, -1, -1, -1, -1, Route::Flag(0), DataType::AUDIO));
+			
+			if (bus->ensure_io (input_channels, output_channels, false, this)) {
+				error << string_compose (_("cannot configure %1 in/%2 out configuration for new audio track"),
+							 input_channels, output_channels)
+				      << endmsg;
+			}
+			
+			for (uint32_t x = 0; x < bus->n_inputs().get(DataType::AUDIO); ++x) {
+				
+				port = "";
+				
+				if (input_auto_connect & AutoConnectPhysical) {
+					port = physinputs[((n+x)%n_physical_inputs)];
+				} 
+				
+				if (port.length() && bus->connect_input (bus->input (x), port, this)) {
+					break;
 				}
 			}
-
-			if (port.length() && bus->connect_output (bus->output (x), port, this)) {
-				break;
+			
+			for (uint32_t x = 0; x < bus->n_outputs().get(DataType::AUDIO); ++x) {
+				
+				port = "";
+				
+				if (output_auto_connect & AutoConnectPhysical) {
+					port = physoutputs[((n+x)%n_physical_outputs)];
+				} else if (output_auto_connect & AutoConnectMaster) {
+					if (_master_out) {
+						port = _master_out->input (x%_master_out->n_inputs().get(DataType::AUDIO))->name();
+					}
+				}
+				
+				if (port.length() && bus->connect_output (bus->output (x), port, this)) {
+					break;
+				}
+			}
+			
+			if (_control_out) {
+				vector<string> cports;
+				uint32_t ni = _control_out->n_inputs().get(DataType::AUDIO);
+				
+				for (uint32_t n = 0; n < ni; ++n) {
+					cports.push_back (_control_out->input(n)->name());
+				}
+				bus->set_control_outs (cports);
 			}
-		}
 
-		if (_control_out) {
-			vector<string> cports;
-			uint32_t ni = _control_out->n_inputs().get(DataType::AUDIO);
+			ret.push_back (bus);
+		}
+	
 
-			for (uint32_t n = 0; n < ni; ++n) {
-				cports.push_back (_control_out->input(n)->name());
-			}
-			bus->set_control_outs (cports);
+		catch (failed_constructor &err) {
+			error << _("Session: could not create new audio route.") << endmsg;
+			ret.clear ();
+			return ret;
 		}
-		
-		add_route (bus);
-		return bus;
+
+		--how_many;
 	}
 
-	catch (failed_constructor &err) {
-		error << _("Session: could not create new audio route.") << endmsg;
-		return shared_ptr<Route> ((Route*) 0);
+	if (!ret.empty()) {
+		add_routes (ret, false);
+		save_state (_current_snapshot_name);
 	}
+
+	return ret;
+
 }
 
 void
-Session::add_route (shared_ptr<Route> route)
+Session::add_routes (RouteList& new_routes, bool save)
 {
 	{ 
 		RCUWriter<RouteList> writer (routes);
 		shared_ptr<RouteList> r = writer.get_copy ();
-		r->push_front (route);
+		r->insert (r->end(), new_routes.begin(), new_routes.end());
 		resort_routes_using (r);
 	}
 
-	route->solo_changed.connect (sigc::bind (mem_fun (*this, &Session::route_solo_changed), route));
-	route->mute_changed.connect (mem_fun (*this, &Session::route_mute_changed));
-	route->output_changed.connect (mem_fun (*this, &Session::set_worst_io_latencies_x));
-	route->redirects_changed.connect (mem_fun (*this, &Session::update_latency_compensation_proxy));
-
-	if (route->master()) {
-		_master_out = route;
-	}
-
-	if (route->control()) {
-		_control_out = route;
+	for (RouteList::iterator x = new_routes.begin(); x != new_routes.end(); ++x) {
+		(*x)->solo_changed.connect (sigc::bind (mem_fun (*this, &Session::route_solo_changed), (*x)));
+		(*x)->mute_changed.connect (mem_fun (*this, &Session::route_mute_changed));
+		(*x)->output_changed.connect (mem_fun (*this, &Session::set_worst_io_latencies_x));
+		(*x)->redirects_changed.connect (mem_fun (*this, &Session::update_latency_compensation_proxy));
+		
+		if ((*x)->master()) {
+			_master_out = (*x);
+		}
+		
+		if ((*x)->control()) {
+			_control_out = (*x);
+		}
 	}
 
 	set_dirty();
-	save_state (_current_snapshot_name);
-	save_history (_current_snapshot_name);
 
-	RouteAdded (route); /* EMIT SIGNAL */
+	if (save) {
+		save_state (_current_snapshot_name);
+	}
+
+	RouteAdded (new_routes); /* EMIT SIGNAL */
 }
 
 void
-Session::add_diskstream (Diskstream* dstream)
+Session::add_diskstream (boost::shared_ptr<Diskstream> dstream)
 {
 	/* need to do this in case we're rolling at the time, to prevent false underruns */
 	dstream->do_refill_with_alloc();
 	
 	{ 
-		Glib::RWLock::WriterLock lm (diskstream_lock);
-		diskstreams.push_back (dstream);
+		RCUWriter<DiskstreamList> writer (diskstreams);
+		boost::shared_ptr<DiskstreamList> ds = writer.get_copy();
+		ds->push_back (dstream);
 	}
 
-	/* take a reference to the diskstream, preventing it from
-	   ever being deleted until the session itself goes away,
-	   or chooses to remove it for its own purposes.
-	*/
-
-	dstream->ref();
 	dstream->set_block_size (current_block_size);
 
 	dstream->PlaylistChanged.connect (sigc::bind (mem_fun (*this, &Session::diskstream_playlist_changed), dstream));
@@ -2095,12 +2198,6 @@ Session::add_diskstream (Diskstream* dstream)
 	diskstream_playlist_changed (dstream);
 
 	dstream->prepare ();
-
-	set_dirty();
-	save_state (_current_snapshot_name);
-        save_history (_current_snapshot_name);
-
-	DiskstreamAdded (dstream); /* EMIT SIGNAL */
 }
 
 void
@@ -2138,20 +2235,19 @@ Session::remove_route (shared_ptr<Route> route)
 	}
 
 	Track* t;
-	Diskstream* ds = 0;
+	boost::shared_ptr<Diskstream> ds;
 	
 	if ((t = dynamic_cast<Track*>(route.get())) != 0) {
-		ds = &t->diskstream();
+		ds = t->diskstream();
 	}
 	
 	if (ds) {
 
 		{
-			Glib::RWLock::WriterLock lm (diskstream_lock);
-			diskstreams.remove (ds);
+			RCUWriter<DiskstreamList> dsl (diskstreams);
+			boost::shared_ptr<DiskstreamList> d = dsl.get_copy();
+			d->remove (ds);
 		}
-
-		ds->unref ();
 	}
 
 	find_current_end ();
@@ -2162,9 +2258,10 @@ Session::remove_route (shared_ptr<Route> route)
 	/* XXX should we disconnect from the Route's signals ? */
 
 	save_state (_current_snapshot_name);
-	save_history (_current_snapshot_name);
 
-	/* all shared ptrs to route should go out of scope here */
+	/* try to cause everyone to drop their references */
+
+	route->drop_references ();
 }	
 
 void
@@ -2403,6 +2500,20 @@ Session::route_by_name (string name)
 }
 
 shared_ptr<Route>
+Session::route_by_id (PBD::ID id)
+{
+	shared_ptr<RouteList> r = routes.reader ();
+
+	for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+		if ((*i)->id() == id) {
+			return *i;
+		}
+	}
+
+	return shared_ptr<Route> ((Route*) 0);
+}
+
+shared_ptr<Route>
 Session::route_by_remote_id (uint32_t id)
 {
 	shared_ptr<RouteList> r = routes.reader ();
@@ -2438,11 +2549,9 @@ Session::get_maximum_extent () const
 	jack_nframes_t max = 0;
 	jack_nframes_t me; 
 
-	/* Don't take the diskstream lock. Caller must have other ways to
-	   ensure atomicity.
-	*/
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::const_iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::const_iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		Playlist* pl = (*i)->playlist();
 		if ((me = pl->get_maximum_extent()) > max) {
 			max = me;
@@ -2452,32 +2561,32 @@ Session::get_maximum_extent () const
 	return max;
 }
 
-Diskstream *
+boost::shared_ptr<Diskstream>
 Session::diskstream_by_name (string name)
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if ((*i)->name() == name) {
-			return* i;
+			return *i;
 		}
 	}
 
-	return 0;
+	return boost::shared_ptr<Diskstream>((Diskstream*) 0);
 }
 
-Diskstream *
+boost::shared_ptr<Diskstream>
 Session::diskstream_by_id (const PBD::ID& id)
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if ((*i)->id() == id) {
 			return *i;
 		}
 	}
 
-	return 0;
+	return boost::shared_ptr<Diskstream>((Diskstream*) 0);
 }
 
 /* Region management */
@@ -2767,10 +2876,10 @@ int
 Session::remove_last_capture ()
 {
 	list<Region*> r;
-
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		list<Region*>& l = (*i)->last_capture_regions();
 		
 		if (!l.empty()) {
@@ -2829,7 +2938,6 @@ Session::remove_source (Source* source)
 		*/
 		
 		save_state (_current_snapshot_name);
-                save_history (_current_snapshot_name);
 	}
 
 	SourceRemoved(source); /* EMIT SIGNAL */
@@ -3404,10 +3512,11 @@ Session::set_all_mute (bool yn)
 uint32_t
 Session::n_diskstreams () const
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
 	uint32_t n = 0;
 
-	for (DiskstreamList::const_iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+	for (DiskstreamList::const_iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if (!(*i)->hidden()) {
 			n++;
 		}
@@ -3426,15 +3535,15 @@ Session::graph_reordered ()
 		return;
 	}
 	
-	Glib::RWLock::ReaderLock lm2 (diskstream_lock);
-
 	resort_routes ();
 
 	/* force all diskstreams to update their capture offset values to 
 	   reflect any changes in latencies within the graph.
 	*/
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->set_capture_offset ();
 	}
 }
@@ -3691,11 +3800,9 @@ Session::remove_named_selection (NamedSelection* named_selection)
 void
 Session::reset_native_file_format ()
 {
-	// jlc - WHY take routelock?
-	//RWLockMonitor lm1 (route_lock, true, __LINE__, __FILE__);
-	Glib::RWLock::ReaderLock lm2 (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->reset_write_sources (false);
 	}
 }
@@ -3792,7 +3899,7 @@ Session::write_one_audio_track (AudioTrack& track, jack_nframes_t start, jack_nf
 	uint32_t         x;
 	char             buf[PATH_MAX+1];
 	string           dir;
-	ChanCount        nchans(track.audio_diskstream().n_channels());
+	ChanCount        nchans(track.audio_diskstream()->n_channels());
 	jack_nframes_t   position;
 	jack_nframes_t   this_chunk;
 	jack_nframes_t   to_do;
@@ -3805,7 +3912,7 @@ Session::write_one_audio_track (AudioTrack& track, jack_nframes_t start, jack_nf
 	
 	/* call tree *MUST* hold route_lock */
 	
-	if ((playlist = track.diskstream().playlist()) == 0) {
+	if ((playlist = track.diskstream()->playlist()) == 0) {
 		goto out;
 	}
 
@@ -4007,3 +4114,14 @@ Session::set_xfade_model (CrossfadeModel xm)
 	}
 }
 
+void
+Session::add_curve(Curve *curve)
+{
+    curves[curve->id()] = curve;
+}
+
+void
+Session::add_automation_list(AutomationList *al)
+{
+    automation_lists[al->id()] = al;
+}
diff --git a/libs/ardour/session_butler.cc b/libs/ardour/session_butler.cc
index 6509a783bb..5d691a7425 100644
--- a/libs/ardour/session_butler.cc
+++ b/libs/ardour/session_butler.cc
@@ -248,11 +248,11 @@ Session::butler_thread_work ()
 
 		gettimeofday (&begin, 0);
 
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader ();
 		
-		for (i = diskstreams.begin(); !transport_work_requested() && butler_should_run && i != diskstreams.end(); ++i) {
+		for (i = dsl->begin(); !transport_work_requested() && butler_should_run && i != dsl->end(); ++i) {
 
-			Diskstream* const ds = *i;
+			boost::shared_ptr<Diskstream> ds = *i;
 
 			switch (ds->do_refill ()) {
 			case 0:
@@ -271,7 +271,7 @@ Session::butler_thread_work ()
 
 		}
 
-		if (i != diskstreams.end()) {
+		if (i != dsl->end()) {
 			/* we didn't get to all the streams */
 			disk_work_outstanding = true;
 		}
@@ -293,7 +293,7 @@ Session::butler_thread_work ()
 		compute_io = true;
 		gettimeofday (&begin, 0);
 
-		for (i = diskstreams.begin(); !transport_work_requested() && butler_should_run && i != diskstreams.end(); ++i) {
+		for (i = dsl->begin(); !transport_work_requested() && butler_should_run && i != dsl->end(); ++i) {
 			// cerr << "write behind for " << (*i)->name () << endl;
 			
 			switch ((*i)->do_flush (Session::ButlerContext)) {
@@ -322,7 +322,7 @@ Session::butler_thread_work ()
 			request_stop ();
 		}
 
-		if (i != diskstreams.end()) {
+		if (i != dsl->end()) {
 			/* we didn't get to all the streams */
 			disk_work_outstanding = true;
 		}
@@ -349,7 +349,7 @@ Session::butler_thread_work ()
 			Glib::Mutex::Lock lm (butler_request_lock);
 
 			if (butler_should_run && (disk_work_outstanding || transport_work_requested())) {
-//				for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+//				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 //					cerr << "AFTER " << (*i)->name() << ": pb = " << (*i)->playback_buffer_load() << " cp = " << (*i)->capture_buffer_load() << endl;
 //				}
 
@@ -388,8 +388,8 @@ Session::overwrite_some_buffers (Diskstream* ds)
 
 	} else {
 
-		Glib::RWLock::ReaderLock dm (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			(*i)->set_pending_overwrite (true);
 		}
 	}
diff --git a/libs/ardour/session_command.cc b/libs/ardour/session_command.cc
index af507208ab..4e7c4151b7 100644
--- a/libs/ardour/session_command.cc
+++ b/libs/ardour/session_command.cc
@@ -2,24 +2,99 @@
 #include <ardour/route.h>
 #include <pbd/memento_command.h>
 #include <ardour/diskstream.h>
+#include <ardour/playlist.h>
+#include <ardour/tempo.h>
+#include <ardour/audiosource.h>
+#include <ardour/audioregion.h>
+#include <pbd/error.h>
+using namespace PBD;
+#include "i18n.h"
+
 
 namespace ARDOUR {
 
+static map<PBD::ID, Stateful*> registry;
+
+void Session::register_with_memento_command_factory(PBD::ID id, Stateful *ptr)
+{
+    registry[id] = ptr;
+}
+    
 Command *Session::memento_command_factory(XMLNode *n)
 {
     PBD::ID id;
-    XMLNode *before, *after;
+    XMLNode *before = 0, *after = 0;
+    XMLNode *child;
+
+    /* get id */
+    id = PBD::ID(n->property("obj_id")->value());
+
+    /* get before/after */
+    if (n->name() == "MementoCommand")
+    {
+        before = new XMLNode(*n->children().front());
+        after = new XMLNode(*n->children().back());
+	child = before;
+    } else if (n->name() == "MementoUndoCommand")
+    {
+        before = new XMLNode(*n->children().front());
+	child = before;
+    }
+    else if (n->name() == "MementoRedoCommand")
+    {
+        after = new XMLNode(*n->children().front());
+	child = after;
+    }
+
+    if (!child)
+    {
+	error << _("Tried to reconstitute a MementoCommand with no contents, failing. id=") << id.to_s() << endmsg;
+	return 0;
+    }
 
-    /* get obj_id */
 
-    /* get before and/or after */
+    /* create command */
+    string obj_T = n->children().front()->name();
+    if (obj_T == "AudioRegion" || obj_T == "MidiRegion" || obj_T == "Region")
+    {
+        if (regions.count(id))
+            return new MementoCommand<Region>(*regions[id], before, after);
+    }
+    else if (obj_T == "Source" || obj_T == "AudioSource" || obj_T == "MidiSource")
+    {
+        if (sources.count(id))
+            return new MementoCommand<Source>(*sources[id], before, after);
+    }
+    else if (obj_T == "Location")
+        return new MementoCommand<Location>(*_locations.get_location_by_id(id), before, after);
+    else if (obj_T == "Locations")
+        return new MementoCommand<Locations>(_locations, before, after);
+    else if (obj_T == "TempoMap")
+        return new MementoCommand<TempoMap>(*_tempo_map, before, after);
+    else if (obj_T == "Playlist" || obj_T == "MidiPlaylist" || obj_T == "AudioPlaylist")
+    {
+        if (Playlist *pl = playlist_by_name(child->property("name")->value()))
+            return new MementoCommand<Playlist>(*pl, before, after);
+    }
+    else if (obj_T == "Route") // inlcudes AudioTrack
+        return new MementoCommand<Route>(*route_by_id(id), before, after);
+    else if (obj_T == "Curve")
+    {
+        if (curves.count(id))
+            return new MementoCommand<Curve>(*curves[id], before, after);
+    }
+    else if (obj_T == "AutomationList")
+    {
+        if (automation_lists.count(id))
+            return new MementoCommand<AutomationList>(*automation_lists[id], before, after);
+    }
+    // For Editor and AutomationLine which are off-limits here
+    else if (registry.count(id))
+        return new MementoCommand<Stateful>(*registry[id], before, after);
 
-    /* get an object by id by trial and error, and use it to construct an
-     * appropriate memento command */
-    // e.g.
-    if (Diskstream *obj = diskstream_by_id(id))
-	return new MementoCommand<Diskstream>(*obj, *before, *after);
-    // etc.
+    /* we failed */
+    error << _("could not reconstitute MementoCommand from XMLNode. id=") << id.to_s() << endmsg;
+    return 0;
 	
 	return 0;
 }
diff --git a/libs/ardour/session_export.cc b/libs/ardour/session_export.cc
index c5449d3e06..946d825c1c 100644
--- a/libs/ardour/session_export.cc
+++ b/libs/ardour/session_export.cc
@@ -496,8 +496,9 @@ Session::prepare_to_export (AudioExportSpecification& spec)
 	/* get everyone to the right position */
 
 	{
-		Glib::RWLock::ReaderLock lm (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if ((*i)-> seek (spec.start_frame, true)) {
 				error << string_compose (_("%1: cannot seek to %2 for export"),
 						  (*i)->name(), spec.start_frame)
diff --git a/libs/ardour/session_midi.cc b/libs/ardour/session_midi.cc
index b0738e95a7..d7cdd94b2b 100644
--- a/libs/ardour/session_midi.cc
+++ b/libs/ardour/session_midi.cc
@@ -605,7 +605,6 @@ Session::mmc_record_strobe (MIDI::MachineControl &mmc)
 		*/
 		
 		save_state ("", true);
-		save_history ("");
 		g_atomic_int_set (&_record_status, Enabled);
 		RecordStateChanged (); /* EMIT SIGNAL */
 		
diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index 6d13caced8..e99478e0b4 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -72,7 +72,8 @@ Session::process (jack_nframes_t nframes)
 void
 Session::prepare_diskstreams ()
 {
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->prepare ();
 	}
 }
@@ -150,7 +151,8 @@ Session::process_routes (jack_nframes_t nframes, jack_nframes_t offset)
 			   call path, so make sure we release any outstanding locks here before we return failure.
 			*/
 
-			for (DiskstreamList::iterator ids = diskstreams.begin(); ids != diskstreams.end(); ++ids) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+			for (DiskstreamList::iterator ids = dsl->begin(); ids != dsl->end(); ++ids) {
 				(*ids)->recover ();
 			}
 
@@ -193,7 +195,8 @@ Session::silent_process_routes (jack_nframes_t nframes, jack_nframes_t offset)
 			   call path, so make sure we release any outstanding locks here before we return failure.
 			*/
 
-			for (DiskstreamList::iterator ids = diskstreams.begin(); ids != diskstreams.end(); ++ids) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+			for (DiskstreamList::iterator ids = dsl->begin(); ids != dsl->end(); ++ids) {
 				(*ids)->recover ();
 			}
 
@@ -212,7 +215,8 @@ Session::commit_diskstreams (jack_nframes_t nframes, bool &needs_butler)
 	float pworst = 1.0f;
 	float cworst = 1.0f;
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 
 		if ((*i)->hidden()) {
 			continue;
@@ -305,12 +309,10 @@ Session::process_with_events (jack_nframes_t nframes)
 	end_frame = _transport_frame + nframes;
 
 	{
-		Glib::RWLock::ReaderLock dsm (diskstream_lock, Glib::TRY_LOCK);
-		
 		Event* this_event;
 		Events::iterator the_next_one;
 		
-		if (!dsm.locked() || (post_transport_work & (PostTransportLocate|PostTransportStop))) {
+		if (post_transport_work & (PostTransportLocate|PostTransportStop)) {
 			no_roll (nframes, 0);
 			return;
 		}
@@ -575,17 +577,17 @@ Session::follow_slave (jack_nframes_t nframes, jack_nframes_t offset)
 		if (slave_state == Waiting) {
 
 			// cerr << "waiting at " << slave_transport_frame << endl;
-			Glib::RWLock::ReaderLock dsm (diskstream_lock, Glib::TRY_LOCK);
-			
-			if (dsm.locked() && slave_transport_frame >= slave_wait_end) {
+			if (slave_transport_frame >= slave_wait_end) {
 				// cerr << "\tstart at " << _transport_frame << endl;
 
 				slave_state = Running;
 
 				bool ok = true;
 				jack_nframes_t frame_delta = slave_transport_frame - _transport_frame;
+
+				boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 				
-				for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 					if (!(*i)->can_internal_playback_seek (frame_delta)) {
 						ok = false;
 						break;
@@ -593,7 +595,7 @@ Session::follow_slave (jack_nframes_t nframes, jack_nframes_t offset)
 				}
 
 				if (ok) {
-					for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+					for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 						(*i)->internal_playback_seek (frame_delta);
 					}
 					_transport_frame += frame_delta;
@@ -697,12 +699,6 @@ Session::follow_slave (jack_nframes_t nframes, jack_nframes_t offset)
 
 		bool need_butler;
 		
-		Glib::RWLock::ReaderLock dsm (diskstream_lock, Glib::TRY_LOCK);
-		if (!dsm.locked()) {
-			goto noroll;
-		}
-
-		
 		prepare_diskstreams ();
 		silent_process_routes (nframes, offset);
 		commit_diskstreams (nframes, need_butler);
@@ -748,9 +744,7 @@ Session::process_without_events (jack_nframes_t nframes)
 	long frames_moved;
 	
 	{
-		Glib::RWLock::ReaderLock dsm (diskstream_lock, Glib::TRY_LOCK);
-
-		if (!dsm.locked() || (post_transport_work & (PostTransportLocate|PostTransportStop))) {
+		if (post_transport_work & (PostTransportLocate|PostTransportStop)) {
 			no_roll (nframes, 0);
 			return;
 		}
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index cefae9dd3d..5553127b90 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -271,8 +271,9 @@ Session::first_stage_init (string fullpath, string snapshot_name)
 	Source::SourceCreated.connect (mem_fun (*this, &Session::add_source));
 	Playlist::PlaylistCreated.connect (mem_fun (*this, &Session::add_playlist));
 	Redirect::RedirectCreated.connect (mem_fun (*this, &Session::add_redirect));
-	Diskstream::DiskstreamCreated.connect (mem_fun (*this, &Session::add_diskstream));
 	NamedSelection::NamedSelectionCreated.connect (mem_fun (*this, &Session::add_named_selection));
+        Curve::CurveCreated.connect (mem_fun (*this, &Session::add_curve));
+        AutomationList::AutomationListCreated.connect (mem_fun (*this, &Session::add_automation_list));
 
 	Controllable::Created.connect (mem_fun (*this, &Session::add_controllable));
 	Controllable::GoingAway.connect (mem_fun (*this, &Session::remove_controllable));
@@ -354,6 +355,7 @@ Session::second_stage_init (bool new_session)
 		_end_location_is_free = false;
 	}
 	
+        restore_history(_current_snapshot_name);
 	return 0;
 }
 
@@ -631,14 +633,15 @@ Session::load_diskstreams (const XMLNode& node)
 	clist = node.children();
 
 	for (citer = clist.begin(); citer != clist.end(); ++citer) {
-		Diskstream* dstream = 0;
 
 		try {
 			/* diskstreams added automatically by DiskstreamCreated handler */
 			if ((*citer)->name() == "AudioDiskstream" || (*citer)->name() == "DiskStream") {
-				dstream = new AudioDiskstream (*this, **citer);
+				boost::shared_ptr<AudioDiskstream> dstream (new AudioDiskstream (*this, **citer));
+				add_diskstream (dstream);
 			} else if ((*citer)->name() == "MidiDiskstream") {
-				dstream = new MidiDiskstream (*this, **citer);
+				boost::shared_ptr<MidiDiskstream> dstream (new MidiDiskstream (*this, **citer));
+				add_diskstream (dstream);
 			} else {
 				error << _("Session: unknown diskstream type in XML") << endmsg;
 			}
@@ -727,6 +730,7 @@ Session::save_state (string snapshot_name, bool pending)
 	}
 
 	if (!pending) {
+                save_history(snapshot_name);
 
 		bool was_dirty = dirty();
 
@@ -1391,8 +1395,8 @@ Session::state(bool full_state)
 	child = node->add_child ("DiskStreams");
 
 	{ 
-		Glib::RWLock::ReaderLock dl (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if (!(*i)->hidden()) {
 				child->add_child_nocopy ((*i)->get_state());
 			}
@@ -1695,7 +1699,6 @@ Session::set_state (const XMLNode& node)
 
 	if (state_was_pending) {
 		save_state (_current_snapshot_name);
-                save_history (_current_snapshot_name);
 		remove_pending_capture_state ();
 		state_was_pending = false;
 	}
@@ -1713,6 +1716,7 @@ Session::load_routes (const XMLNode& node)
 {
 	XMLNodeList nlist;
 	XMLNodeConstIterator niter;
+	RouteList new_routes;
 
 	nlist = node.children();
 
@@ -1727,9 +1731,11 @@ Session::load_routes (const XMLNode& node)
 			return -1;
 		}
 
-		add_route (route);
+		new_routes.push_back (route);
 	}
 
+	add_routes (new_routes);
+
 	return 0;
 }
 
@@ -2599,7 +2605,6 @@ void
 Session::auto_save()
 {
 	save_state (_current_snapshot_name);
-        save_history (_current_snapshot_name);
 }
 
 RouteGroup *
@@ -3270,7 +3275,6 @@ Session::cleanup_sources (Session::cleanup_report& rep)
 	*/
 	
 	save_state ("");
-	save_history ("");
 
   out:
 	_state_of_the_state = (StateOfTheState) (_state_of_the_state & ~InCleanup);
@@ -3410,6 +3414,7 @@ Session::save_history (string snapshot_name)
     string xml_path;
     string bak_path;
 
+
     tree.set_root (&history.get_state());
 
     if (snapshot_name.empty()) {
@@ -3417,6 +3422,7 @@ Session::save_history (string snapshot_name)
     }
 
     xml_path = _path + snapshot_name + ".history"; 
+    cerr << "Saving history to " << xml_path << endmsg;
 
     bak_path = xml_path + ".bak";
 
@@ -3450,3 +3456,65 @@ Session::save_history (string snapshot_name)
 
     return 0;
 }
+
+int
+Session::restore_history (string snapshot_name)
+{
+    XMLTree tree;
+    string xmlpath;
+
+    /* read xml */
+    xmlpath = _path + snapshot_name + ".history";
+    cerr << string_compose(_("Loading history from '%1'."), xmlpath) << endmsg;
+
+    if (access (xmlpath.c_str(), F_OK)) {
+        error << string_compose(_("%1: session history file \"%2\" doesn't exist!"), _name, xmlpath) << endmsg;
+        return 1;
+    }
+
+    if (!tree.read (xmlpath)) {
+        error << string_compose(_("Could not understand ardour file %1"), xmlpath) << endmsg;
+        return -1;
+    }
+
+    /* replace history */
+    history.clear();
+    for (XMLNodeConstIterator it  = tree.root()->children().begin();
+         it != tree.root()->children().end();
+         it++)
+    {
+        XMLNode *t = *it;
+        UndoTransaction ut;
+        struct timeval tv;
+
+        ut.set_name(t->property("name")->value());
+        stringstream ss(t->property("tv_sec")->value());
+        ss >> tv.tv_sec;
+        ss.str(t->property("tv_usec")->value());
+        ss >> tv.tv_usec;
+        ut.set_timestamp(tv);
+
+        for (XMLNodeConstIterator child_it  = t->children().begin();
+             child_it != t->children().end();
+             child_it++)
+        {
+            XMLNode *n = *child_it;
+            Command *c;
+            if (n->name() == "MementoCommand" ||
+                n->name() == "MementoUndoCommand" ||
+                n->name() == "MementoRedoCommand")
+            {
+                c = memento_command_factory(n);
+                if (c)
+                    ut.add_command(c);
+            }
+            else
+            {
+                error << string_compose(_("Couldn't figure out how to make a Command out of a %1 XMLNode."), n->name()) << endmsg;
+            }
+        }
+        history.add(ut);
+    }
+
+    return 0;
+}
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index aad3617580..85e2dd391f 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -197,8 +197,8 @@ Session::realtime_stop (bool abort)
 void
 Session::butler_transport_work ()
 {
-	Glib::RWLock::ReaderLock dsm (diskstream_lock);
 	boost::shared_ptr<RouteList> r = routes.reader ();
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
 	if (post_transport_work & PostTransportCurveRealloc) {
 		for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
@@ -207,7 +207,7 @@ Session::butler_transport_work ()
 	}
 
 	if (post_transport_work & PostTransportInputChange) {
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			(*i)->non_realtime_input_change ();
 		}
 	}
@@ -223,7 +223,7 @@ Session::butler_transport_work ()
 		cumulative_rf_motion = 0;
 		reset_rf_scale (0);
 
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if (!(*i)->hidden()) {
 				if ((*i)->speed() != 1.0f || (*i)->speed() != -1.0f) {
 					(*i)->seek ((jack_nframes_t) (_transport_frame * (double) (*i)->speed()));
@@ -253,9 +253,9 @@ Session::butler_transport_work ()
 void
 Session::non_realtime_set_speed ()
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->non_realtime_set_speed ();
 	}
 }
@@ -263,9 +263,9 @@ Session::non_realtime_set_speed ()
 void
 Session::non_realtime_overwrite ()
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if ((*i)->pending_overwrite) {
 			(*i)->overwrite_existing_buffers ();
 		}
@@ -281,7 +281,9 @@ Session::non_realtime_stop (bool abort)
 	
 	did_record = false;
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if ((*i)->get_captured_frames () != 0) {
 			did_record = true;
 			break;
@@ -329,14 +331,14 @@ Session::non_realtime_stop (bool abort)
                         XMLNode &before = loc->get_state();
                         loc->set_end(_transport_frame);
                         XMLNode &after = loc->get_state();
-                        add_command (new MementoCommand<Location>(*loc, before, after));
+                        add_command (new MementoCommand<Location>(*loc, &before, &after));
 		}
 
 		_end_location_is_free = false;
 		_have_captured = true;
 	}
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->transport_stopped (*now, xnow, abort);
 	}
 	
@@ -375,7 +377,7 @@ Session::non_realtime_stop (bool abort)
 	}
 #endif
 
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if (!(*i)->hidden()) {
 				if ((*i)->speed() != 1.0f || (*i)->speed() != -1.0f) {
 					(*i)->seek ((jack_nframes_t) (_transport_frame * (double) (*i)->speed()));
@@ -413,7 +415,6 @@ Session::non_realtime_stop (bool abort)
 	if ((post_transport_work & PostTransportLocate) && get_record_enabled()) {
 		/* capture start has been changed, so save pending state */
 		save_state ("", true);
-                save_history ("");
 	}
 
         /* always try to get rid of this */
@@ -424,7 +425,6 @@ Session::non_realtime_stop (bool abort)
 
 	if (did_record) {
 		save_state (_current_snapshot_name);
-		save_history (_current_snapshot_name);
 	}
 
 	if (post_transport_work & PostTransportDuration) {
@@ -501,7 +501,8 @@ Session::set_auto_loop (bool yn)
 
 			if (seamless_loop) {
 				// set all diskstreams to use internal looping
-				for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+				boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 					if (!(*i)->hidden()) {
 						(*i)->set_loop (loc);
 					}
@@ -509,7 +510,8 @@ Session::set_auto_loop (bool yn)
 			}
 			else {
 				// set all diskstreams to NOT use internal looping
-				for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+				boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 					if (!(*i)->hidden()) {
 						(*i)->set_loop (0);
 					}
@@ -539,7 +541,8 @@ Session::set_auto_loop (bool yn)
 		clear_events (Event::AutoLoop);
 
 		// set all diskstreams to NOT use internal looping
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if (!(*i)->hidden()) {
 				(*i)->set_loop (0);
 			}
@@ -657,12 +660,10 @@ Session::locate (jack_nframes_t target_frame, bool with_roll, bool with_flush, b
 	if (with_roll) {
 		/* switch from input if we're going to roll */
 		if (Config->get_use_hardware_monitoring()) {
-			/* Even though this is called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					//cerr << "switching from input" << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (!auto_input);
@@ -672,12 +673,9 @@ Session::locate (jack_nframes_t target_frame, bool with_roll, bool with_flush, b
 	} else {
 		/* otherwise we're going to stop, so do the opposite */
 		if (Config->get_use_hardware_monitoring()) {
-			/* Even though this is called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					//cerr << "switching to input" << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (true);
@@ -718,12 +716,9 @@ Session::set_transport_speed (float speed, bool abort)
 
 		if (Config->get_use_hardware_monitoring())
 		{
-			/* Even though this is called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					//cerr << "switching to input" << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (true);	
@@ -744,12 +739,10 @@ Session::set_transport_speed (float speed, bool abort)
 		}
 
 		if (Config->get_use_hardware_monitoring()) {
-			/* Even though this is called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if (auto_input && (*i)->record_enabled ()) {
 					//cerr << "switching from input" << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (false);	
@@ -800,7 +793,8 @@ Session::set_transport_speed (float speed, bool abort)
 		_last_transport_speed = _transport_speed;
 		_transport_speed = speed;
 		
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if ((*i)->realtime_set_speed ((*i)->speed(), true)) {
 				post_transport_work = PostTransportWork (post_transport_work | PostTransportSpeed);
 			}
@@ -890,7 +884,8 @@ Session::actually_start_transport ()
 	transport_sub_state |= PendingDeclickIn;
 	_transport_speed = 1.0;
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->realtime_set_speed ((*i)->speed(), true);
 	}
 
@@ -1023,7 +1018,8 @@ Session::set_slave_source (SlaveSource src, jack_nframes_t frame)
 	
 	_slave_type = src;
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if (!(*i)->hidden()) {
 			if ((*i)->realtime_set_speed ((*i)->speed(), true)) {
 				non_rt_required = true;
@@ -1214,7 +1210,6 @@ Session::update_latency_compensation (bool with_stop, bool abort)
 		return;
 	}
 
-	Glib::RWLock::ReaderLock lm2 (diskstream_lock);
 	_worst_track_latency = 0;
 
 	boost::shared_ptr<RouteList> r = routes.reader ();
@@ -1252,7 +1247,9 @@ Session::update_latency_compensation (bool with_stop, bool abort)
 	/* reflect any changes in latencies into capture offsets
 	*/
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->set_capture_offset ();
 	}
 }
diff --git a/libs/ardour/smf_source.cc b/libs/ardour/smf_source.cc
index bd5649bc2e..5a5bafb6ca 100644
--- a/libs/ardour/smf_source.cc
+++ b/libs/ardour/smf_source.cc
@@ -294,7 +294,7 @@ SMFSource::read_event(MidiEvent& ev) const
 jack_nframes_t
 SMFSource::read_unlocked (MidiRingBuffer& dst, jack_nframes_t start, jack_nframes_t cnt, jack_nframes_t stamp_offset) const
 {
-	cerr << "SMF - read " << start << " -- " << cnt;
+	//cerr << "SMF - read " << start << " -- " << cnt;
 
 	jack_nframes_t time = 0;
 
@@ -312,12 +312,12 @@ SMFSource::read_unlocked (MidiRingBuffer& dst, jack_nframes_t start, jack_nframe
 	while (!feof(_fd)) {
 		int ret = read_event(ev);
 		if (ret == -1) { // EOF
-			cerr << "SMF - EOF\n";
+			//cerr << "SMF - EOF\n";
 			break;
 		}
 
 		if (ret == 0) { // meta-event (skipped)
-			cerr << "SMF - META\n";
+			//cerr << "SMF - META\n";
 			time += ev.time; // just accumulate delta time and ignore event
 			continue;
 		}
@@ -370,7 +370,7 @@ SMFSource::read_unlocked (MidiRingBuffer& dst, jack_nframes_t start, jack_nframe
 jack_nframes_t
 SMFSource::write_unlocked (MidiRingBuffer& src, jack_nframes_t cnt)
 {
-	cerr << "SMF WRITE -- " << _length << "--" << cnt << endl;
+	//cerr << "SMF WRITE -- " << _length << "--" << cnt << endl;
 	
 	MidiBuffer buf(1024); // FIXME: allocation, size?
 	src.read(buf, /*_length*/0, _length + cnt); // FIXME?
diff --git a/libs/ardour/track.cc b/libs/ardour/track.cc
index 28816541f1..a96a4a1a82 100644
--- a/libs/ardour/track.cc
+++ b/libs/ardour/track.cc
@@ -41,7 +41,6 @@ using namespace PBD;
 
 Track::Track (Session& sess, string name, Route::Flag flag, TrackMode mode, DataType default_type)
 	: Route (sess, name, 1, -1, -1, -1, flag, default_type)
-	, _diskstream (0)
 	,  _rec_enable_control (*this)
 {
 	_declickable = true;
@@ -52,7 +51,6 @@ Track::Track (Session& sess, string name, Route::Flag flag, TrackMode mode, Data
 
 Track::Track (Session& sess, const XMLNode& node, DataType default_type)
 	: Route (sess, "to be renamed", 0, 0, -1, -1, Route::Flag(0), default_type)
-	, _diskstream (0)
 	, _rec_enable_control (*this)
 {
 	_freeze_record.state = NoFreeze;
@@ -62,9 +60,6 @@ Track::Track (Session& sess, const XMLNode& node, DataType default_type)
 
 Track::~Track ()
 {
-	if (_diskstream) {
-		_diskstream->unref();
-	}
 }
 
 void
@@ -224,7 +219,6 @@ Track::set_name (string str, void *src)
 
 	if ((ret = IO::set_name (str, src)) == 0) {
 		_session.save_state ("");
-		_session.save_history ("");
 	}
 	return ret;
 }
diff --git a/libs/pbd/id.cc b/libs/pbd/id.cc
index 0de0d052c3..ab7806873e 100644
--- a/libs/pbd/id.cc
+++ b/libs/pbd/id.cc
@@ -25,7 +25,7 @@ ID::init ()
 ID::ID ()
 {
 	Glib::Mutex::Lock lm (*counter_lock);
-	id = _counter++;
+	_id = _counter++;
 }
 
 ID::ID (string str)
@@ -36,14 +36,14 @@ ID::ID (string str)
 int
 ID::string_assign (string str)
 {
-	return sscanf (str.c_str(), "%" PRIu64, &id) != 0;
+	return sscanf (str.c_str(), "%" PRIu64, &_id) != 0;
 }
 
 void
 ID::print (char* buf) const
 {
 	/* XXX sizeof buf is unknown. bad API design */
-	snprintf (buf, 16, "%" PRIu64, id);
+	snprintf (buf, 16, "%" PRIu64, _id);
 }
 
 string ID::to_s() const
@@ -61,10 +61,10 @@ ID::operator= (string str)
 }
 
 ostream&
-operator<< (ostream& ostr, const ID& id)
+operator<< (ostream& ostr, const ID& _id)
 {
 	char buf[32];
-	id.print (buf);
+	_id.print (buf);
 	ostr << buf;
 	return ostr;
 }
diff --git a/libs/pbd/pbd/abstract_ui.cc b/libs/pbd/pbd/abstract_ui.cc
index 0e34787a2d..eca53916af 100644
--- a/libs/pbd/pbd/abstract_ui.cc
+++ b/libs/pbd/pbd/abstract_ui.cc
@@ -4,6 +4,10 @@
 #include <pbd/pthread_utils.h>
 #include <pbd/failed_constructor.h>
 
+#include "i18n.h"
+
+using namespace std;
+
 template <typename RequestObject>
 AbstractUI<RequestObject>::AbstractUI (string name, bool with_signal_pipes)
 	: BaseUI (name, with_signal_pipes)
@@ -44,7 +48,7 @@ AbstractUI<RequestObject>::get_request (RequestType rt)
 	if (rbuf == 0) {
 		/* Cannot happen, but if it does we can't use the error reporting mechanism */
 		cerr << _("programming error: ")
-		     << string_compose (X_("no %1-UI request buffer found for thread %2"), name(), pthread_name())
+		     << string_compose ("no %1-UI request buffer found for thread %2", name(), pthread_name())
 		     << endl;
 		abort ();
 	}
@@ -55,7 +59,7 @@ AbstractUI<RequestObject>::get_request (RequestType rt)
 
 	if (vec.len[0] == 0) {
 		if (vec.len[1] == 0) {
-			cerr << string_compose (X_("no space in %1-UI request buffer for thread %2"), name(), pthread_name())
+			cerr << string_compose ("no space in %1-UI request buffer for thread %2", name(), pthread_name())
 			     << endl;
 			return 0;
 		} else {
@@ -131,7 +135,7 @@ AbstractUI<RequestObject>::send_request (RequestObject *req)
 			   thread isn't registered!
 			*/
 			cerr << _("programming error: ")
-			     << string_compose (X_("AbstractUI::send_request() called from %1, but no request buffer exists for that thread"), pthread_name())
+			     << string_compose ("AbstractUI::send_request() called from %1 (%2), but no request buffer exists for that thread", name(), pthread_name())
 			     << endl;
 			abort ();
 		}
diff --git a/libs/pbd/pbd/destructible.h b/libs/pbd/pbd/destructible.h
new file mode 100644
index 0000000000..126bd04bba
--- /dev/null
+++ b/libs/pbd/pbd/destructible.h
@@ -0,0 +1,20 @@
+#ifndef __pbd_destructible_h__
+#define __pbd_destructible_h__
+
+#include <sigc++/signal.h>
+
+namespace PBD {
+
+class Destructible {
+  public:
+	Destructible() {}
+	virtual ~Destructible () {}
+
+	sigc::signal<void> GoingAway;
+
+	void drop_references () const { GoingAway(); }
+};
+
+}
+
+#endif /* __pbd_destructible_h__ */
diff --git a/libs/pbd/pbd/id.h b/libs/pbd/pbd/id.h
index 1ce448d58b..c110362734 100644
--- a/libs/pbd/pbd/id.h
+++ b/libs/pbd/pbd/id.h
@@ -14,17 +14,17 @@ class ID {
 	ID (std::string);
 	
 	bool operator== (const ID& other) const {
-		return id == other.id; 
+		return _id == other._id; 
 	}
 
 	bool operator!= (const ID& other) const {
-		return id != other.id;
+		return _id != other._id;
 	}
 
 	ID& operator= (std::string); 
 
 	bool operator< (const ID& other) const {
-		return id < other.id;
+		return _id < other._id;
 	}
 
 	void print (char* buf) const;
@@ -35,7 +35,7 @@ class ID {
 	static void init ();
 
   private:
-	uint64_t id;
+	uint64_t _id;
 	int string_assign (std::string);
 
 	static Glib::Mutex* counter_lock;
diff --git a/libs/pbd/pbd/memento_command.h b/libs/pbd/pbd/memento_command.h
index 122dcb4c86..3a72fc9841 100644
--- a/libs/pbd/pbd/memento_command.h
+++ b/libs/pbd/pbd/memento_command.h
@@ -36,70 +36,44 @@ class MementoCommand : public Command
     public:
 	MementoCommand(XMLNode &state);
         MementoCommand(obj_T &obj, 
-                       XMLNode &before,
-                       XMLNode &after
+                       XMLNode *before,
+                       XMLNode *after
                        ) 
             : obj(obj), before(before), after(after) {}
-        void operator() () { obj.set_state(after); }
-        void undo() { obj.set_state(before); }
+        void operator() () 
+        {
+            if (after)
+                obj.set_state(*after); 
+        }
+        void undo() 
+        { 
+            if (before)
+                obj.set_state(*before); 
+        }
         virtual XMLNode &get_state() 
         {
-            XMLNode *node = new XMLNode("MementoCommand");
+            string name;
+            if (before && after)
+                name = "MementoCommand";
+            else if (before)
+                name = "MementoUndoCommand";
+            else
+                name = "MementoRedoCommand";
+
+            XMLNode *node = new XMLNode(name);
             node->add_property("obj_id", obj.id().to_s());
             node->add_property("type_name", typeid(obj).name());
-            node->add_child_copy(before);
-            node->add_child_copy(after);
+
+            if (before)
+                node->add_child_copy(*before);
+            if (after)
+                node->add_child_copy(*after);
+
             return *node;
         }
     protected:
         obj_T &obj;
-        XMLNode &before, &after;
-};
-
-template <class obj_T>
-class MementoUndoCommand : public Command
-{
-public:
-    MementoUndoCommand(XMLNode &state);
-    MementoUndoCommand(obj_T &obj, 
-                       XMLNode &before)
-        : obj(obj), before(before) {}
-    void operator() () { /* noop */ }
-    void undo() { obj.set_state(before); }
-    virtual XMLNode &get_state() 
-    {
-        XMLNode *node = new XMLNode("MementoUndoCommand");
-        node->add_property("obj_id", obj.id().to_s());
-	node->add_property("type_name", typeid(obj).name());
-        node->add_child_copy(before);
-        return *node;
-    }
-protected:
-    obj_T &obj;
-    XMLNode &before;
-};
-
-template <class obj_T>
-class MementoRedoCommand : public Command
-{
-public:
-    MementoRedoCommand(XMLNode &state);
-    MementoRedoCommand(obj_T &obj, 
-                       XMLNode &after)
-        : obj(obj), after(after) {}
-    void operator() () { obj.set_state(after); }
-    void undo() { /* noop */ }
-    virtual XMLNode &get_state()
-    {
-        XMLNode *node = new XMLNode("MementoRedoCommand");
-        node->add_property("obj_id", obj.id().to_s());
-	node->add_property("type_name", typeid(obj).name());
-        node->add_child_copy(after);
-        return *node;
-    }
-protected:
-    obj_T &obj;
-    XMLNode &after;
+        XMLNode *before, *after;
 };
 
 #endif // __lib_pbd_memento_h__
diff --git a/libs/pbd/pbd/rcu.h b/libs/pbd/pbd/rcu.h
index 58a92a206a..e81db8ba87 100644
--- a/libs/pbd/pbd/rcu.h
+++ b/libs/pbd/pbd/rcu.h
@@ -5,8 +5,7 @@
 #include "glibmm/thread.h"
  
 #include <list> 
- 
- 
+
 template<class T>
 class RCUManager
 {
@@ -43,7 +42,7 @@ public:
  
 	}
  
-	virtual boost::shared_ptr<T> write_copy ()
+	boost::shared_ptr<T> write_copy ()
 	{
 		m_lock.lock();
 
@@ -64,11 +63,11 @@ public:
 		current_write_old = RCUManager<T>::m_rcu_value;
 		
 		boost::shared_ptr<T> new_copy (new T(**current_write_old));
-		
+
 		return new_copy;
 	}
  
-	virtual bool update (boost::shared_ptr<T> new_value)
+	bool update (boost::shared_ptr<T> new_value)
 	{
 		// we hold the lock at this point effectively blocking
 		// other writers.
@@ -98,6 +97,11 @@ public:
 
 		return ret;
 	}
+
+	void flush () {
+		Glib::Mutex::Lock lm (m_lock);
+		m_dead_wood.clear ();
+	}
  
 private:
 	Glib::Mutex			 m_lock;
diff --git a/libs/pbd/pbd/stateful.h b/libs/pbd/pbd/stateful.h
index 3038f16b4f..5adddfc1c0 100644
--- a/libs/pbd/pbd/stateful.h
+++ b/libs/pbd/pbd/stateful.h
@@ -22,6 +22,7 @@
 #define __pbd_stateful_h__
 
 #include <string>
+#include <pbd/id.h>
 
 class XMLNode;
 
@@ -41,10 +42,12 @@ class Stateful {
 
 	virtual void add_instant_xml (XMLNode&, const std::string& dir);
 	XMLNode *instant_xml (const std::string& str, const std::string& dir);
+        PBD::ID id() { return _id; }
 
   protected:
 	XMLNode *_extra_xml;
 	XMLNode *_instant_xml;
+        PBD::ID _id;
 };
 
 #endif /* __pbd_stateful_h__ */
diff --git a/libs/pbd/pbd/unknown_type.h b/libs/pbd/pbd/unknown_type.h
new file mode 100644
index 0000000000..fddc1aeddb
--- /dev/null
+++ b/libs/pbd/pbd/unknown_type.h
@@ -0,0 +1,11 @@
+#ifndef __pbd_unknown_type_h__
+#define __pbd_unknown_type_h__
+
+#include <exception>
+
+class unknown_type : public std::exception {
+  public:
+	virtual const char *what() const throw() { return "unknown type"; }
+};
+
+#endif /* __pbd_unknown_type_h__ */
diff --git a/libs/pbd/undo.cc b/libs/pbd/undo.cc
index 8d1b416c16..6f421de84e 100644
--- a/libs/pbd/undo.cc
+++ b/libs/pbd/undo.cc
@@ -23,6 +23,7 @@
 #include <pbd/undo.h>
 #include <pbd/xml++.h>
 #include <string>
+#include <sstream>
 
 using namespace std;
 using namespace sigc;
@@ -87,6 +88,13 @@ UndoTransaction::redo ()
 XMLNode &UndoTransaction::get_state()
 {
     XMLNode *node = new XMLNode ("UndoTransaction");
+    stringstream ss;
+    ss << _timestamp.tv_sec;
+    node->add_property("tv_sec", ss.str());
+    ss.str("");
+    ss << _timestamp.tv_usec;
+    node->add_property("tv_usec", ss.str());
+    node->add_property("name", _name);
 
     list<Command*>::iterator it;
     for (it=actions.begin(); it!=actions.end(); it++)
diff --git a/libs/surfaces/control_protocol/basic_ui.cc b/libs/surfaces/control_protocol/basic_ui.cc
index bee4783914..3dc93cc64a 100644
--- a/libs/surfaces/control_protocol/basic_ui.cc
+++ b/libs/surfaces/control_protocol/basic_ui.cc
@@ -145,7 +145,6 @@ void
 BasicUI::save_state ()
 {
 	session->save_state ("");
-        session->save_history("");
 }
 
 void