Orchestra Fountain

Water fountains sequenced to create displays choreographed to music are widely known to exist. This takes it a step further and has that sequenced, choreographed water display actually create the music by using the force of the water to activate various not creating mechanisms. Others here have posted having water make "leaves" vibrate and ring or trigger piano keys, this would be a whole orchestra, drums, bells, strings and woodwinds.

Drums and bells: This one's easy, water droplets drop onto them making them boom or ring.

Strings: You could get single notes the same way you'd trigger the drums or bells, and you might even be able to "bow" strings like you would a cello or violin by spraying them with a high pressure water stream. If this worked you could vary the pressure of the stream to have the notes fade in and out.

Woodwinds: The trickiest, not sure if you'd be able to move enough air with a water stream... hmm, could just have the water push air I suppose. Okay, just have an empty tube of air aimed at the particular tuned tube's whistle portion and blow the air out with a column of water. When the water hits the whistle portion it'll just stop playing, the tube will empty at the other end and fill with the next load of air to be pushed by the water column, so yea, you could get wind instruments too.

You've obviously have lights matching the mood of the particular phrase as well. Red for minor notes, blue for major, etc. Or whatever worked. Could also have this played by people in real time using keys with variable pressure control or sliders as needed.

If I built this the first piece would obviously be the Blue Danube.