I've done some work to flesh out the Pd MIDI handling so all messages come through. I also found and fixed a pretty major bug in Portmidi on macOS which has been accepted upstream where Pm hangs when receiving a realtime message during a running status byte situation.

See: https://github.com/pure-data/pure-data/pull/214

and my test program: https://github.com/danomatika/miditester

I've tested on macOS and all values are coming in and out correctly. This needs to be tested on Linux and Windows.

I also went a bit crazy and implemented song select, song position, and time code objects but that got out of hand a bit as MTC is more complicated then I originally thought. This work is in a separate branch and not included in the PR above.