MIDI Library v3.2 (MIDI.h)

http://playground.arduino.cc/Main/MIDILibrary -- This library enables MIDI I/O communications on the Arduino serial ports. You can send and receive messages of all kind (including System Exclusive, RealTime etc..). The purpose of this library is not to make a big synthetizer out of an Arduino board, the application remains yours. However, it will help you interfacing it with other MIDI devices.