This is designed by Steve Mann, the wearable computer guy, and his research team.
From their paper describing the invention:
Unlike a piano keyboard in which the keys reach a point of maximal displacement, our keys are essentially infinite in length, and thus never reach an end to their key travel.
The hydraulophone combines the intricate embouchure control of woodwind instruments with the polyphony of keyboard instruments.
40 seconds. Link to Video
And, yes, that is Pachelbel’s Canon. It’s everywhere.
The instrument in the video is installed at the Ontario Science Centre.
Hacked Gadgets has a lot of pictures and videos.
