This is a neat little project -- a totally homemade MIDI Concertina controller (which if you aren't too hip on musical instruments is like a smaller more portable Accordion). This doesn't make any sounds on it's own, but it can send commands to a MIDI sound generator box that can.

A neat improvement would be a hinge between the two halves, and some sort of sensor to detect opening/closing of the two halves so that you could send velocity information to the MIDI box, which would give you a lot more expressiveness.

Regardless, this looks like a lot of fun for about $30 in parts.