Artist Max Björverud rigged a bunch of toilet paper dispensers to sound like a choir. Yeah, he started this project a long time before we became obsessed with toilet paper. The "instrument" is explained at Hack a Day.
Inspired by the way bicycle computers determine your speed, [Max] took a set of toilet paper holders, extended each roll holding part with a 3D-printed attachment housing a magnet, and installed a Hall-effect sensor to determine the rolling activity. The rolls’ sensor data is then collected with an Arduino Mega and passed on to a Raspberry Pi Zero running Pure Data, creating the actual sounds.(via Neatorama)