http://www.fpga4fun.com/MusicBox.html
https://github.com/vishnubob/python-midi/
http://www.blitter.com/~russtopia/MIDI/~jglatt/
https://en.wikipedia.org/wiki/General_MIDI
http://nickfever.com/music/midi-cc-list
http://www.onicos.com/staff/iz/formats/midi-event.html
http://www.ccarh.org/courses/253/handout/smf/
http://www.recordingblogs.com/sa/tabid/88/Default.aspx?topic=MIDI+Set+Tempo+meta+message
http://www.lastrayofhope.co.uk/2009/12/23/midi-delta-time-ticks-to-seconds/