David Bowen is a robotic sculptor. By that I mean he makes robotic sculptures, not that he himself is a robot--at least to the best of my knowledge. And not that there's anything wrong with being a robot--I'm no robophobe, mind you.
But I digress. Bowen made a robot that plays a piano. He installed it at the L'Assaut de la Menuiserie, an art gallery in Saint-Étienne, France. A camera mounted on the roof of the building noted the presence of clouds. As clouds flowed over, the robot played keys, thus playing a naturally occurring music in the sky.