Saw this colored peg low res image and was reminded again I want to do something similar with black and white ping pong balls. I would work up a Lego bot to drop the balls in.
And then I had a cooler idea–I’ve seen a programmed water drop device used to make images. A related idea would be to drop water onto piano strings. The drops would strike the strings and make sound instead of images. The drops would fall a distance so you would see the music visually–see the notes coming before they hit.
Thinking more, there’s a good chance this wouldn’t work–the water drops wouldn’t have enough force. Worth a try though. :)