Inspired by the CGI video series Animusic, Stefan “g000ze” of Lets Make Robots and his sons built this Marblephone. Using a bunch of marbles, some solenoids, and bars from a xylophone, he built an electromechanical instrument to play out tunes by dropping marbles onto the xylophone bars. It looks like the piece is actually a few years old, and he is just getting back to adding an automatic conveyor belt to recycle the dropped marbles. Looks fun!
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Kind of sounds like music made by an old time pinball machine.