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. Types and basic operation 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. Those described in Mann's paper Hydraulophone design considerations use water jets striking perforated spinning disks, shafts, or valves, to create a pulsating water flow, similar to a siren disk. A single disk, shaft, or valve assembly can have rings or passages with different numbers of holes for different notes. Some hydraulophones have reeds (one or more reed for each finger hole) and some are reedless, having one or more fipple mechanism associated with each finger hole, thus having no moving parts to wear out. Blocking flow through a finger hole directs the water instead to one or more of the above-described sound-production mechanisms, or resulting changes in flow or pressure affect a separate sounding mechanism associated with each finger hole. Blocking water from coming out of a given hole produces a given note, which, in some embodiments, is electrically amplified by a hydrophone. In one embodiment there is a further processing of each hydrophone signal. Embodiments with various kinds of acoustic or optical pickups are also disclosed. Some hydraulophones include an underwater hydrophone pickup to allow the sounds produced by the water to be electrically amplified. Electric amplification allows effects to be added (as with an electric guitar) as well as making the hydraulophone a hyper-acoustic instrument (that is, using computation to change the acoustic sound of the water into some other instrument). Embouchure The water must be "blown" into the hydraulophone by way of a pump which can be hand-operated, wind operated, water powered, or electric. Unlike woodwind instruments in which there is one mouthpiece at the entrance to the flute chamber, hydraulophones have mouthpieces at every exit