György Ligeti’s Poeme Symphonique is a piece for 100 metronomes. Set at various tempi, they’re all started at once, and then left to go until they wind down, eventually thinning out and producing rhythms from the dense and chaotic beginning. Classic Ligeti stuff here.

Click ahead to 1:30 in the video to see them start. (Although if I remember correctly, this is supposed to be the first piece in a concert, started before the doors are opened, so it runs as people are sitting down. The fancy starting contraption in the video is neat though!)

Another random fact I learned about this piece: it actually requires some practice to set up, because it is very easy to wind the metronomes up so far that they go for a very very long time.