Scanning a handheld magnetic pickup back and forth over the piano strings makes a pretty neat sound. I may try attaching a rail on which the pickup can slide back and forth. The pickup is plugged into an ordinary guitar amp. Plug: Fun with Sensors workshop this Saturday at NYC Resistor!
I’ve always thought the patterns on corncobs looked like player piano rolls. So I wrote a program that watches a slowly-turning corncob. Whenever a particularly dark kernel crosses the centerline of the image, it plays a note corresponding to the height. You can download the Processing code from moonmilk.com/11/02/cornscan.txt.