Homemade Robotic Xylophone Plays Holiday Melodies

Quick video shortcuts:

60-second demo of the xylophone playing itself: http://www.youtube.com/watch?v=sR3xmof8rZY#t=11m50s

Machining our own solenoids on our lathe: http://www.youtube.com/watch?v=sR3xmof8rZY#t=5m5s

Fun fact for the programming-minded folks: Songs are programmed in with C macros. GCC kept trying to inline the note-queueing function, but that bloated the compiled program size tremendously (despite specifying -Os on the command line). We had to use a GCC directive to force it not to inline...

This is very impressive and I appreciate the engineering education to boot.