A hydraulophone is a tonal acoustic musical instrument played by direct physical contact with water (sometimes other fluids) where sound is generated or affected hydraulically.

The hydraulophone was described and named by Steve Mann in 2005, and patented in 2011. Typically, sound is produced by the same hydraulic fluid in contact with the player's fingers. It has been used as a sensory exploration device for low-vision individuals.

The term may be applied based on the interface used to play the instrument, in which a player blocks the flow of water through a particular hole in order to sound a particular note, or based on a hydraulic sound production mechanism.

Hydraulophones use water-flow sound-producing mechanisms. They have a user interface, which is blocking water jets to produce sound.

The hydraulophone is similar to a woodwind instrument, but it runs on incompressible (or less compressible) fluid rather than a compressible gas like air. In this context hydraulophones are sometimes called "woodwater" instruments regardless of whether or not they are made of wood (as woodwind instruments are often not made of wood).

Presently the world's largest hydraulophone is the main architectural centerpiece out in front of the Ontario Science Centre, one of Canada's landmark architecture sites. It is also Toronto's only freely accessible aquatic play facility that runs 24 hours a day.

This hydraulophone is not put on display during winter months.

More Info: en.wikipedia.org