diff --git a/libs/backends/coreaudio/coreaudio_backend.cc b/libs/backends/coreaudio/coreaudio_backend.cc
index b3459511fb..0e978bff71 100644
--- a/libs/backends/coreaudio/coreaudio_backend.cc
+++ b/libs/backends/coreaudio/coreaudio_backend.cc
@@ -1577,7 +1577,7 @@ CoreAudioBackend::process_callback (const uint32_t n_samples, const uint64_t hos
 	pre_process();
 
 	// cycle-length in usec
-	const int64_t nominal_time = 1e6 * n_samples / _samplerate;
+	const double nominal_time = 1e6 * n_samples / _samplerate;
 
 	clock1 = g_get_monotonic_time();
 
@@ -1627,10 +1627,15 @@ CoreAudioBackend::process_callback (const uint32_t n_samples, const uint64_t hos
 	/* queue outgoing midi */
 	i = 0;
 	for (std::vector<CoreBackendPort*>::const_iterator it = _system_midi_out.begin (); it != _system_midi_out.end (); ++it, ++i) {
+#if 0 // something's still b0rked with CoreMidiIo::send_events()
+		const CoreMidiBuffer *src = static_cast<const CoreMidiPort*>(*it)->const_buffer();
+		_midiio->send_events (i, nominal_time, (void*)src);
+#else // works..
 		const CoreMidiBuffer *src = static_cast<const CoreMidiPort*>(*it)->const_buffer();
 		for (CoreMidiBuffer::const_iterator mit = src->begin (); mit != src->end (); ++mit) {
 			_midiio->send_event (i, (*mit)->timestamp() / nominal_time, (*mit)->data(), (*mit)->size());
 		}
+#endif
 	}
 
 	/* write back audio */
@@ -1644,7 +1649,7 @@ CoreAudioBackend::process_callback (const uint32_t n_samples, const uint64_t hos
 	/* calc DSP load. */
 	clock2 = g_get_monotonic_time();
 	const int64_t elapsed_time = clock2 - clock1;
-	_dsp_load = elapsed_time / (float) nominal_time;
+	_dsp_load = elapsed_time / nominal_time;
 
 	pthread_mutex_unlock (&_process_callback_mutex);
 	return 0;
diff --git a/libs/backends/coreaudio/coremidi_io.cc b/libs/backends/coreaudio/coremidi_io.cc
index 365bde9457..8b6bad82e8 100644
--- a/libs/backends/coreaudio/coremidi_io.cc
+++ b/libs/backends/coreaudio/coremidi_io.cc
@@ -20,6 +20,7 @@
 #include <CoreAudio/HostTime.h>
 
 #include "coremidi_io.h"
+#include "coreaudio_backend.h"
 
 using namespace ARDOUR;
 
@@ -36,13 +37,16 @@ static void midiInputCallback(const MIDIPacketList *list, void *procRef, void *s
 	}
 	RingBuffer<uint8_t> * rb  = static_cast<RingBuffer < uint8_t > *> (srcRef);
 	if (!rb) return;
-	for (UInt32 i = 0; i < list->numPackets; i++) {
-		const MIDIPacket *packet = &list->packet[i];
-		if (rb->write_space() < sizeof(MIDIPacket)) {
+	MIDIPacket const *p = &list->packet[0];
+	for (UInt32 i = 0; i < list->numPackets; ++i) {
+		uint32_t len = ((p->length + 3)&~3) + sizeof(MIDITimeStamp) + sizeof(UInt16);
+		if (rb->write_space() < sizeof(uint32_t) + len) {
 			fprintf(stderr, "CoreMIDI: dropped MIDI event\n");
 			continue;
 		}
-		rb->write((uint8_t*)packet, sizeof(MIDIPacket));
+		rb->write ((uint8_t*)&len, sizeof(uint32_t));
+		rb->write ((uint8_t*)p, len);
+		p = MIDIPacketNext (p);
 	}
 }
 
@@ -176,10 +180,16 @@ CoreMidiIo::recv_event (uint32_t port, double cycle_time_us, uint64_t &time, uin
 	}
 	assert(port < _n_midi_in);
 
-	while (_rb[port]->read_space() >= sizeof(MIDIPacket)) {
+	const size_t minsize = 1 + sizeof(uint32_t) + sizeof(MIDITimeStamp) + sizeof(UInt16);
+
+	while (_rb[port]->read_space() > minsize) {
 		MIDIPacket packet;
-		size_t rv = _rb[port]->read((uint8_t*)&packet, sizeof(MIDIPacket));
-		assert(rv == sizeof(MIDIPacket));
+		size_t rv;
+		uint32_t s = 0;
+		rv = _rb[port]->read((uint8_t*)&s, sizeof(uint32_t));
+		assert(rv == sizeof(uint32_t));
+		rv = _rb[port]->read((uint8_t*)&packet, s);
+		assert(rv == s);
 		_input_queue[port].push_back(boost::shared_ptr<CoreMIDIPacket>(new _CoreMIDIPacket (&packet)));
 	}
 
@@ -212,6 +222,40 @@ CoreMidiIo::recv_event (uint32_t port, double cycle_time_us, uint64_t &time, uin
 	return 0;
 }
 
+int
+CoreMidiIo::send_events (uint32_t port, double timescale, const void *b)
+{
+	if (!_active || _time_at_cycle_start == 0) {
+		return 0;
+	}
+
+	assert(port < _n_midi_out);
+	const UInt64 ts = AudioConvertHostTimeToNanos(_time_at_cycle_start);
+
+	const CoreMidiBuffer *src = static_cast<CoreMidiBuffer const *>(b);
+
+	int32_t bytes[8192]; // int for alignment
+	MIDIPacketList *mpl = (MIDIPacketList*)bytes;
+	MIDIPacket *cur = MIDIPacketListInit(mpl);
+
+	for (CoreMidiBuffer::const_iterator mit = src->begin (); mit != src->end (); ++mit) {
+		assert((*mit)->size() < 256);
+		cur = MIDIPacketListAdd(mpl, sizeof(bytes), cur,
+				AudioConvertNanosToHostTime(ts + (*mit)->timestamp() / timescale),
+				(*mit)->size(), (*mit)->data());
+		if (!cur) {
+#ifndef DEBUG
+			printf("CoreMidi: Packet list overflow, dropped events\n");
+#endif
+			break;
+		}
+	}
+	if (mpl->numPackets > 0) {
+		MIDISend(_output_ports[port], _output_endpoints[port], mpl);
+	}
+	return 0;
+}
+
 int
 CoreMidiIo::send_event (uint32_t port, double reltime_us, const uint8_t *d, const size_t s)
 {
diff --git a/libs/backends/coreaudio/coremidi_io.h b/libs/backends/coreaudio/coremidi_io.h
index b5eda1c2fd..21806ab4fd 100644
--- a/libs/backends/coreaudio/coremidi_io.h
+++ b/libs/backends/coreaudio/coremidi_io.h
@@ -75,6 +75,7 @@ public:
 	void start_cycle ();
 
 	int send_event (uint32_t, double, const uint8_t *, const size_t);
+	int send_events (uint32_t, double, const void *);
 	size_t recv_event (uint32_t, double, uint64_t &, uint8_t *, size_t &);
 
 	uint32_t n_midi_inputs (void) const { return _n_midi_in; }