MIDI Physical Layer:
http://www.personal.kent.edu/~sbirch/Music_Production/MP-II/MIDI/midi_physical_layer.htm
MIDI Message Table:
http://www.midi.org/techspecs/midimessages.php
MIDI Electrical Specification:
http://www.midi.org/techspecs/electrispec.php
Arduino MIDI-in shield:
http://www.instructables.com/id/Arduino-MIDI-in-shield/
MPLABX IDE:
http://www.microchip.com/pagehandler/en-us/family/mplabx/