Earlier this year, I started building a midi-controlled automatic drum player. It converts a channel of midi data to drumstick movements.
Here is where I am so far. The final version will be able to control twelve drum components simultaneously.
The central unit houses a custom programmed arduino-based microcontroller which processes the midi data, controling the powerflow from the 600W power source to the various solenoids.
(video made with iPhone 4S)