I sat down last night at a friend's house and I had my laptop out trying to write some music. I say trying because without a (midi)keyboard I find that composing becomes much more difficult. So I figured that a good project would be a midi keyboard on the actuall keyboard. And this is what I did. It plays nine octaves (four higher and four lower than middle C) and supports all 128 GM MIDI instruments. It even has the ability to attatch to external MIDI devices.
While it has almost not GUI, it does have functionality.
1 - 9: Change Octaves (Middle C is the letter 'A' in octave 5)
SPACE: Sustain Pedal
UP: Change Instrument+1
RIGHT: Change Instrument+10
DOWN: Change Instrument-1
LEFT: Change Instrument-10
Let me know of any problems!