Using SunSPOT microcontrollers and actuators, we created a self-playing glockenspiel. The microcontrollers take MIDI files as input and use them to control solenoids, which strike the instrument.
I created a kit which safely converts a computer power supply to a bench supply. There are many guides online for how to do this, but it requires opening the supply, snipping off wires, and soldering them back together. I designed a PCB and an enclosure for the device, and now you can use an existing supply without destroying it.