Anyone interested in marble devices/kinetic sculptures (and music) should check out the Wintergatan YouTube channel: https://www.youtube.com/user/wintergatan2000
. Swedish musician Martin Molin is designing and building a marble-based music machine that he hopes will go on tour with his band some day. He is very meticulous in his process and I find the whole thing fascinating. Worth checking out, though by now there are many, many videos to watch. He also has videos of some other of his inventions and explorations along his journey.