Yes, look it up om the arduino forums.
I couple of quick URLs from my arduino tab:
http://vusb.wikidot.com/start
https://github.com/adafruit/Adafruit_ProTrinket_Bootloader
Or use a Teensy -
http://www.pjrc.com/teensy/
or -
http://www.pjrc.com/teensy/td_midi.html
I'm using one in a midi to 1V/oct analog synth driver that I hacked together.