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 reeds for each finger hole) and some are reedless, having one or more fipple mechanisms 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 port from the chamber. Whereas internal ducted flutes have one fipple mechanism for the mouth of the player, along with several finger holes that share the one fipple mechanism, the hydraulophone has a separate mouth/mouthpiece for each finger hole. A typical park hydraulophone for installation in public spaces has 12 mouths, whereas a concert hydraulophone typically has 45 mouths. Embouchure is controlled by way of the instrument's mouth, not the player's mouth such that the player can sing along with the hydraulophone (i.e. a player can sing and play the instrument at the same time). Moreover, the instrument provides the unique capability of polyphonic embouchure, where a player can dynamically "sculpt" each note by the shape and position of each finger inserted into each of the mouths. For example, the sound is different when fingering the center of a water jet than when fingering the water jet near the periphery of the circular mouth's opening.
Relationships to other instruments
Woodwind 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).
Pipe organ Many hydraulophones include a separate water-filled pipe for each note, and have sound-production means similar to pipe organs (but with water rather than air), while maintaining the flute like user interface (finger embouchure holes). This form of hydraulophone is similar to an organ, but has water flowing through the pipes instead of air flowing through the pipes.
Piano On a concert hydraulophone, the finger holes are arranged like the keys on a piano, i.e. there is a row of uniformly spaced holes close to the player, and a row of holes that are in groups of 2, 3, 2, 3, ..., a little further from the player. Whereas the piano and organ both have a similar kind of keyboard layout, the response ("key action") is different. Pianos tend to respond to velocity (how quickly a key is struck), whereas organs tend to respond to displacement (whether or not a key is pressed down). Hydraulophones tend to respond to the time-integral of displacement (total water flow), as well as to displacement, velocity, and to some degree jerk and jounce.
Instruments that use other states of water
The hydraulophone uses liquid, typically water. However, other instruments utilize water in other physical states. The pagophone is an idiophone (similar to the xylophone) that uses bars made from frozen water. The calliope is a variation of the pipe organ which passes pressurized steam through large whistles.
12-jet diatonic Many diatonic hydraulophones are built with 12 water jets, one for each of the instrument's 12 notes. The standard compass starts on A, extending up an octave and a half to E.
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