Go to the woods of Kyushu, Japan.

Engineer a massive  marimba to run down the slope of a forested hill. Take a wooden ball, place it at the top of said instrument, and push it. What do you get? Bach’s treatment of a traditional church hymn! Namely, “Jesu, Joy of Man’s Desiring.”

and here is how it was done-

A spectacular feat of engineering and creativity. And just guess what inspired its making?

Some time ago, I had the idea of having a railing which you could run a stick along, which would play a tune in the same way, and the railing turned into a maze. (You would be able to find your way out by “playing” the tune. Managed to get the local council interested and even had a park lined up, but alas, the funding fell through!
This is just a lovely idea and brought to my attention by Eli Kassner – thanks Eli!

PS If your Japanese is up to it, here is a TED talk from the creator behind the project. Shake your mind!