diff --git a/gtk2_ardour/editor_drag.cc b/gtk2_ardour/editor_drag.cc
index 25a0fd1885..30211049c6 100644
--- a/gtk2_ardour/editor_drag.cc
+++ b/gtk2_ardour/editor_drag.cc
@@ -3768,7 +3768,6 @@ NoteDrag::motion (GdkEvent*, bool)
                                                                cnote->note()->length(), 
                                                                cnote->note()->note() + drag_delta_note,
                                                                cnote->note()->velocity()));
-                bool overlaps = cnote->region_view().midi_region()->model()->overlaps (check_note, cnote->note());
 
 		region->move_selection (dx, dy);
 
diff --git a/libs/ardour/amp.cc b/libs/ardour/amp.cc
index ceb593f4c3..a739b59088 100644
--- a/libs/ardour/amp.cc
+++ b/libs/ardour/amp.cc
@@ -167,9 +167,8 @@ Amp::apply_gain (BufferSet& bufs, nframes_t nframes, gain_t initial, gain_t targ
 			Evoral::MIDIEvent<MidiBuffer::TimeType> ev = *m;
 
 			if (ev.is_note_on()) {
-				gain_t scale = delta * (ev.time()/nframes);
-				std::cerr << "scale by " << scale << " for " << ev.time() << " of " << nframes << std::endl;
-				ev.scale_velocity (scale);
+				gain_t scale = delta * (ev.time()/(double) nframes);
+				ev.scale_velocity (initial+scale);
 			}
 		}
 	}
diff --git a/libs/ardour/audio_port.cc b/libs/ardour/audio_port.cc
index a75f7d7a09..71ec7c6289 100644
--- a/libs/ardour/audio_port.cc
+++ b/libs/ardour/audio_port.cc
@@ -98,8 +98,8 @@ AudioPort::get_audio_buffer (nframes_t nframes, nframes_t offset)
 }
 
 size_t
-AudioPort::raw_buffer_size(nframes_t nframes) const
+AudioPort::raw_buffer_size (nframes_t nframes) const
 {
-	return nframes * sizeof(float);
+	return nframes * sizeof (Sample);
 }
 
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index a16f268edd..d2cf8d12a4 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -232,6 +232,15 @@ AudioEngine::start ()
 		}
 
 		_raw_buffer_sizes[DataType::AUDIO] = blocksize * sizeof(float);
+
+                jack_port_t* midi_port = jack_port_register (_priv_jack, "m", JACK_DEFAULT_MIDI_TYPE, JackPortIsOutput, 0);
+                if (!midi_port) {
+                        error << _("Cannot create temporary MIDI port to determine MIDI buffer size") << endmsg;
+                } else {
+                        _raw_buffer_sizes[DataType::MIDI] = jack_midi_max_event_size (jack_port_get_buffer(midi_port, blocksize));
+                        cerr << "MIDI port buffers = " << _raw_buffer_sizes[DataType::MIDI] << endl;
+                        jack_port_unregister (_priv_jack, midi_port);
+                }
 	}
 
 	return _running ? 0 : -1;
@@ -420,6 +429,7 @@ AudioEngine::process_thread ()
                 jack_nframes_t nframes = jack_cycle_wait (_jack);
 
                 if (process_callback (nframes)) {
+                        cerr << "--- process\n";
                         return 0;
                 }
 
@@ -583,16 +593,40 @@ AudioEngine::_bufsize_callback (nframes_t nframes, void *arg)
 int
 AudioEngine::jack_bufsize_callback (nframes_t nframes)
 {
+        bool need_midi_size = true;
+        bool need_audio_size = true;
+
 	_buffer_size = nframes;
-	_raw_buffer_sizes[DataType::AUDIO] = nframes * sizeof(float);
-	cout << "FIXME: Assuming maximum MIDI buffer size " << nframes * 4 << "bytes" << endl;
-	_raw_buffer_sizes[DataType::MIDI] = nframes * 4;
 	_usecs_per_cycle = (int) floor ((((double) nframes / frame_rate())) * 1000000.0);
 	last_monitor_check = 0;
 
 	boost::shared_ptr<Ports> p = ports.reader();
 
+        /* crude guesses, see below where we try to get the right answers.
+
+           Note that our guess for MIDI deliberatey tries to overestimate
+           by a little. It would be nicer if we could get the actual
+           size from a port, but we have to use this estimate in the 
+           event that there are no MIDI ports currently. If there are
+           the value will be adjusted below.
+         */
+
+        _raw_buffer_sizes[DataType::AUDIO] = nframes * sizeof (Sample);
+        _raw_buffer_sizes[DataType::MIDI] = nframes * 4 - (nframes/2);
+
 	for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
+
+                if (need_audio_size && (*i)->type() == DataType::AUDIO) {
+                        _raw_buffer_sizes[DataType::AUDIO] = (*i)->raw_buffer_size (nframes);
+                        need_audio_size = false;
+                }
+                
+                        
+                if (need_midi_size && (*i)->type() == DataType::MIDI) {
+                        _raw_buffer_sizes[DataType::MIDI] = (*i)->raw_buffer_size (nframes);
+                        need_midi_size = false;
+                }
+                
 		(*i)->reset();
 	}
 
diff --git a/libs/ardour/delivery.cc b/libs/ardour/delivery.cc
index d815a06b4f..cb8dc539a2 100644
--- a/libs/ardour/delivery.cc
+++ b/libs/ardour/delivery.cc
@@ -446,7 +446,7 @@ Delivery::flush (nframes_t nframes, nframes64_t time)
 	/* io_lock, not taken: function must be called from Session::process() calltree */
 
 	PortSet& ports (_output->ports());
-
+        
 	for (PortSet::iterator i = ports.begin(); i != ports.end(); ++i) {
 		(*i).flush_buffers (nframes, time, _output_offset);
 	}
diff --git a/libs/ardour/graph.cc b/libs/ardour/graph.cc
index 4cb8d56da4..5e62ba0d6f 100644
--- a/libs/ardour/graph.cc
+++ b/libs/ardour/graph.cc
@@ -220,7 +220,7 @@ Graph::rechain (boost::shared_ptr<RouteList> routelist)
 
         pthread_mutex_lock (&_swap_mutex);
         int chain = _setup_chain;
-        printf ("============== setup %d\n", chain);
+        DEBUG_TRACE (DEBUG::Graph, string_compose ("============== setup %1\n", chain));
         // set all refcounts to 0;
 
         _init_finished_refcount[chain] = 0;
@@ -393,21 +393,21 @@ Graph::dump (int chain)
 
         chain = _pending_chain;
 
-        printf ("--------------------------------------------Graph dump:\n" );
+        DEBUG_TRACE (DEBUG::Graph, "--------------------------------------------Graph dump:\n");
         for (ni=_nodes_rt[chain].begin(); ni!=_nodes_rt[chain].end(); ni++) {
                 boost::shared_ptr<Route> rp = boost::dynamic_pointer_cast<Route>( *ni);
-                printf ("GraphNode: %s  refcount: %d\n", rp->name().c_str(), (*ni)->_init_refcount[chain] );
+                DEBUG_TRACE (DEBUG::Graph, string_compose ("GraphNode: %1  refcount: %2\n", rp->name().c_str(), (*ni)->_init_refcount[chain]));
                 for (ai=(*ni)->_activation_set[chain].begin(); ai!=(*ni)->_activation_set[chain].end(); ai++) {
-                        printf ("  triggers: %s\n", boost::dynamic_pointer_cast<Route>(*ai)->name().c_str() );
+                        DEBUG_TRACE (DEBUG::Graph, string_compose ("  triggers: %1\n", boost::dynamic_pointer_cast<Route>(*ai)->name().c_str()));
                 }
         }
 
-        printf ("------------- trigger list:\n" );
+        DEBUG_TRACE (DEBUG::Graph, "------------- trigger list:\n");
         for (ni=_init_trigger_list[chain].begin(); ni!=_init_trigger_list[chain].end(); ni++) {
-                printf ("GraphNode: %s  refcount: %d\n", boost::dynamic_pointer_cast<Route>(*ni)->name().c_str(), (*ni)->_init_refcount[chain] );
+                DEBUG_TRACE (DEBUG::Graph, string_compose ("GraphNode: %1  refcount: %2\n", boost::dynamic_pointer_cast<Route>(*ni)->name().c_str(), (*ni)->_init_refcount[chain]));
         }
 
-        printf ("final activation refcount: %d\n", _init_finished_refcount[chain] );
+        DEBUG_TRACE (DEBUG::Graph, string_compose ("final activation refcount: %1\n", _init_finished_refcount[chain]));
 #endif
 }
 
diff --git a/libs/ardour/midi_buffer.cc b/libs/ardour/midi_buffer.cc
index cbf7603c96..8299d811f6 100644
--- a/libs/ardour/midi_buffer.cc
+++ b/libs/ardour/midi_buffer.cc
@@ -18,11 +18,17 @@
 */
 
 #include <iostream>
+
 #include "pbd/malign.h"
+#include "pbd/compose.h"
+#include "pbd/debug.h"
+
+#include "ardour/debug.h"
 #include "ardour/midi_buffer.h"
 
 using namespace std;
 using namespace ARDOUR;
+using namespace PBD;
 
 // FIXME: mirroring for MIDI buffers?
 MidiBuffer::MidiBuffer(size_t capacity)
@@ -93,7 +99,10 @@ MidiBuffer::read_from (const Buffer& src, nframes_t nframes, nframes_t dst_offse
 		const Evoral::MIDIEvent<TimeType> ev(*i, false);
 		if (ev.time() >= src_offset && ev.time() < (nframes+src_offset)) {
 			push_back (ev);
-		}
+		} else {
+                        cerr << "MIDI event @ " <<  ev.time() << " skipped, not within range " << src_offset << " .. " 
+                             << (nframes + src_offset) << endl;
+                }
 	}
 
 	_silent = src.silent();
@@ -128,7 +137,7 @@ MidiBuffer::push_back(const Evoral::MIDIEvent<TimeType>& ev)
 		cerr << "MidiBuffer::push_back failed (buffer is full)" << endl;
 		return false;
 	}
-
+        
 	if (!Evoral::midi_event_is_valid(ev.buffer(), ev.size())) {
 		cerr << "WARNING: MidiBuffer ignoring illegal MIDI event" << endl;
 		return false;
@@ -147,8 +156,22 @@ bool
 MidiBuffer::push_back(TimeType time, size_t size, const uint8_t* data)
 {
 	const size_t stamp_size = sizeof(TimeType);
-	/*cerr << "MidiBuffer: pushing event @ " << ev.time()
-		<< " size = " << ev.size() << endl;*/
+
+#ifndef NDEBUG
+                DEBUG_STR_DECL(a);
+                DEBUG_STR_APPEND(a, string_compose ("midibuffer %1 push event @ %2 sz %3 ", this, time, size));
+		for (size_t i=0; i < size; ++i) {
+			DEBUG_STR_APPEND(a,hex);
+			DEBUG_STR_APPEND(a,"0x");
+			DEBUG_STR_APPEND(a,(int)data[i]);
+                        DEBUG_STR_APPEND(a,' ');
+		}
+                DEBUG_STR_APPEND(a,'\n');
+                DEBUG_TRACE (DEBUG::MidiIO, DEBUG_STR(a).str());
+#endif
+
+	// cerr << "MidiBuffer: pushing event @ " << time
+        // << " size = " << size << endl;
 
 	if (_size + stamp_size + size >= _capacity) {
 		cerr << "MidiBuffer::push_back failed (buffer is full)" << endl;
@@ -302,10 +325,12 @@ MidiBuffer::merge_in_place(const MidiBuffer &other)
 			++them;
 		}
 
+#if 0                
 		if (us != end())
 			cerr << "us @ " << (*us).time() << endl;
 		if (them != other.end())
 			cerr << "them @ " << (*them).time() << endl;
+#endif
 
 		if (sz) {
 			assert(src >= 0);
@@ -342,7 +367,7 @@ MidiBuffer::merge_in_place(const MidiBuffer &other)
 	size_t test_final_count = 0;
 	test_time = 0;
 	for (iterator i = begin(); i != end(); ++i) {
-		cerr << "CHECK " << test_final_count << " / " << test_us_count + test_them_count << endl;
+		// cerr << "CHECK " << test_final_count << " / " << test_us_count + test_them_count << endl;
 		assert(Evoral::midi_event_is_valid((*i).buffer(), (*i).size()));
 		assert((*i).time() >= test_time);
 		test_time = (*i).time();
diff --git a/libs/ardour/midi_playlist.cc b/libs/ardour/midi_playlist.cc
index eec0cde0db..89b5914753 100644
--- a/libs/ardour/midi_playlist.cc
+++ b/libs/ardour/midi_playlist.cc
@@ -163,11 +163,11 @@ MidiPlaylist::read (MidiRingBuffer<nframes_t>& dst, nframes_t start, nframes_t d
 				DEBUG_TRACE (DEBUG::MidiPlaylistIO, "\tBEFORE: new tracker\n");
 			} else {
 				tracker = t->second;
-				DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("\tBEFORE: tracker says there are %1 on notes", tracker->on()));
+				DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("\tBEFORE: tracker says there are %1 on notes\n", tracker->on()));
 			}
 
 			mr->read_at (dst, start, dur, chan_n, _note_mode, tracker);
-			DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("\tAFTER: tracker says there are %1 on notes", tracker->on()));
+			DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("\tAFTER: tracker says there are %1 on notes\n", tracker->on()));
 
 			if (new_tracker) {
 				pair<Region*,MidiStateTracker*> newpair;
diff --git a/libs/ardour/midi_port.cc b/libs/ardour/midi_port.cc
index 8dddc39fe3..40cb48f54f 100644
--- a/libs/ardour/midi_port.cc
+++ b/libs/ardour/midi_port.cc
@@ -137,8 +137,14 @@ MidiPort::flush_buffers (nframes_t nframes, nframes64_t time, nframes_t offset)
 			assert(ev.time() < (nframes+offset+_port_offset));
 
 			if (ev.time() >= offset + _port_offset) {
-				jack_midi_event_write (jack_buffer, (jack_nframes_t) ev.time(), ev.buffer(), ev.size());
-			}
+				if (jack_midi_event_write (jack_buffer, (jack_nframes_t) ev.time(), ev.buffer(), ev.size()) != 0) {
+                                        cerr << "write failed, drop flushed note off on the floor, time " << ev.time() << " > " << offset << " + " << _port_offset 
+                                             << endl;			
+                                }
+                        } else {
+                                cerr << "drop flushed note off on the floor, time " << ev.time() << " > " << offset << " + " << _port_offset 
+                                     << endl;
+                        }
 		}
 	}
 }
diff --git a/libs/ardour/midi_ring_buffer.cc b/libs/ardour/midi_ring_buffer.cc
index e8ae9bb5d3..2999621b70 100644
--- a/libs/ardour/midi_ring_buffer.cc
+++ b/libs/ardour/midi_ring_buffer.cc
@@ -50,7 +50,7 @@ MidiRingBuffer<T>::read(MidiBuffer& dst, nframes_t start, nframes_t end, nframes
 
 		this->full_peek(sizeof(T), (uint8_t*)&ev_time);
 
-		if (ev_time > end) {
+		if (ev_time >= end) {
 			DEBUG_TRACE (DEBUG::MidiDiskstreamIO, string_compose ("MRB event @ %1 past end @ %2\n", ev_time, end));
 			break;
 		} else if (ev_time < start) {
@@ -70,7 +70,7 @@ MidiRingBuffer<T>::read(MidiBuffer& dst, nframes_t start, nframes_t end, nframes
 		if (ev_type == LoopEventType) {
 			/*ev_time -= start;
 			  ev_time += offset;*/
-			// cerr << "MRB loop boundary @ " << ev_time << endl;
+			cerr << "MRB loop boundary @ " << ev_time << endl;
 
 			// Return without reading data or writing to buffer (loop events have no data)
 			// FIXME: This is not correct, loses events after the loop this cycle
@@ -98,7 +98,7 @@ MidiRingBuffer<T>::read(MidiBuffer& dst, nframes_t start, nframes_t end, nframes
 		// write the timestamp to address (write_loc - 1)
 		uint8_t* write_loc = dst.reserve(ev_time, ev_size);
 		if (write_loc == NULL) {
-			// cerr << "MRB: Unable to reserve space in buffer, event skipped";
+			cerr << "MRB: Unable to reserve space in buffer, event skipped";
 			this->skip (ev_size); // Advance read pointer to next event
 			continue;
 		}
@@ -107,15 +107,16 @@ MidiRingBuffer<T>::read(MidiBuffer& dst, nframes_t start, nframes_t end, nframes
 		success = read_contents (ev_size, write_loc);
 
 #ifndef NDEBUG
-		DEBUG_TRACE (DEBUG::MidiDiskstreamIO, "wrote MidiEvent to Buffer: ");
+                DEBUG_STR_DECL(a);
+                DEBUG_STR_APPEND(a, string_compose ("wrote MidiEvent to Buffer (time=%1, start=%2 offset=%3)", ev_time, start, offset));
 		for (size_t i=0; i < ev_size; ++i) {
-			DEBUG_STR_DECL(a);
 			DEBUG_STR_APPEND(a,hex);
 			DEBUG_STR_APPEND(a,"0x");
 			DEBUG_STR_APPEND(a,(int)write_loc[i]);
-			DEBUG_TRACE (DEBUG::MidiDiskstreamIO, DEBUG_STR(a).str());
+                        DEBUG_STR_APPEND(a,' ');
 		}
-		DEBUG_TRACE (DEBUG::MidiDiskstreamIO, "\n");
+                DEBUG_STR_APPEND(a,'\n');
+                DEBUG_TRACE (DEBUG::MidiDiskstreamIO, DEBUG_STR(a).str());
 #endif
 
 		if (success) {
diff --git a/libs/ardour/midi_track.cc b/libs/ardour/midi_track.cc
index fbd1f54213..d25a70d819 100644
--- a/libs/ardour/midi_track.cc
+++ b/libs/ardour/midi_track.cc
@@ -25,6 +25,7 @@
 
 #include "ardour/amp.h"
 #include "ardour/buffer_set.h"
+#include "ardour/debug.h"
 #include "ardour/delivery.h"
 #include "ardour/io_processor.h"
 #include "ardour/meter.h"
@@ -412,8 +413,12 @@ MidiTrack::write_out_of_band_data (BufferSet& bufs, sframes_t /*start*/, sframes
 {
 	// Append immediate events
 	MidiBuffer& buf (bufs.get_midi (0));
-	_immediate_events.read (buf, 0, 0, nframes - 1); // all stamps = 0
-
+        if (_immediate_events.read_space()) {
+                DEBUG_TRACE (DEBUG::MidiIO, string_compose ("%1 has %2 of immediate events to deliver\n", 
+                                                            name(), _immediate_events.read_space()));
+        }
+	_immediate_events.read (buf, 0, 1, nframes-1); // all stamps = 0
+        
 	// MIDI thru: send incoming data "through" output
 	if (_midi_thru && _session.transport_speed() != 0.0f && _input->n_ports().n_midi()) {
 		buf.merge_in_place (_input->midi(0)->get_midi_buffer(nframes));
@@ -474,6 +479,7 @@ MidiTrack::set_note_mode (NoteMode m)
 void
 MidiTrack::midi_panic()
 {
+        DEBUG_TRACE (DEBUG::MidiIO, string_compose ("%1 delivers panic data\n", name()));
 	for (uint8_t channel = 0; channel <= 0xF; channel++) {
 		uint8_t ev[3] = { MIDI_CMD_CONTROL | channel, MIDI_CTL_SUSTAIN, 0 };
 		write_immediate_event(3, ev);
diff --git a/libs/ardour/port.cc b/libs/ardour/port.cc
index 6ae0c5d92b..5f29503fb6 100644
--- a/libs/ardour/port.cc
+++ b/libs/ardour/port.cc
@@ -316,3 +316,4 @@ Port::physically_connected () const
 
         return false;
 }
+
diff --git a/libs/midi++2/midi++/jack.h b/libs/midi++2/midi++/jack.h
index b720166b49..0433e4ae45 100644
--- a/libs/midi++2/midi++/jack.h
+++ b/libs/midi++2/midi++/jack.h
@@ -30,6 +30,7 @@
 
 #include <glibmm/thread.h>
 
+#include <jack/weakjack.h>
 #include <jack/jack.h>
 #include <jack/midiport.h>