The latest XKCD made me think...

... you could rig up a robotic tapping machine, with prodding metallic fingers, to tap at a given object, such as a desk, or a collection of tin pans. It would first record the sound made by each one, and then work out which note each tap made, and then proceed to play a series of old-timey musical numbers to delight and amuse.

This post was originally on LiveJournal.