In the woods of Kyushu, Japan, a team of filmmakers built a massive xylophone running down a long, steady slope. They then rolled a wooden ball down the thing, striking each tuned bar only once, and it played Bach's "Jesu, Joy of Man's Desiring." (If you're not familiar with the tune, here's an orchestral performance.) This is truly impressive engineering, filmmaking, and music!
Note that at the end it's revealed that it's a cell phone commercial, but I think we can appreciate it as a work of art. The music starts around 0:45, though the first little bit of setup is interesting.
And here's the making-of video, with plenty of trial-and-error (note the careful tuning of the bars while they're still in the shop; also the ending—trying to nail that ball landing is tough!):
Playing Bach on a Giant Forest Xylophone
Jesu, Joy of Man's Desiring