Midignusbuino
The Midignusbuino is a plug-n-play USB-MIDI device that can be used to build MIDI controllers. Most operating systems have built in MIDI support, so no drivers are needed, and almost any music software understands MIDI… It is built on the Gnusbuino platform, is more or less compatible with the Arduino environment and can be programmed through the Arduino IDE
Building / Installing
Hardware schematics and source code are in the SV repository at http://gnusb.svn.sourceforge.net/viewvc/gnusb/branches/gnusbuino/