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Article

Hugh Davies

revised by Andrei Smirnov

[Polyrhythmophone]

Electronic percussion instrument constructed for the composer Henry Cowell by Lev Termen (Leon Theremin) in 1931; two examples were built. It was the earliest electronic rhythm machine. A series of rotating wheels interrupted beams of light to produce very complex rhythms with precision. The polyphonic keyboard had 17 keys, each of which, except the 17th, produced a single note repeated in a periodic rhythm for as long as it was held down; the 17th key inserted an extra beat in the middle of each bar. Each of the 16 rhythms could be produced individually or in combination, requiring 455 days, 2 hours, and 30 minutes to play all possible combinations, assuming a duration of 10 seconds for each.

Successive keys did not produce a chromatic scale but notes in the overtone series of the lowest note; similarly the periodic rhythm of each note was a successively higher multiple of that produced by the lowest. For example, two keys at the bottom of the keyboard which on a normal keyboard would sound an interval of a major 6th, on the Rhythmicon sounded an interval of three octaves and a whole tone, and the upper note repeated nine times faster than the lower; if the configuration were moved up a ‘semitone’ the interval was two octaves and a major 6th and the upper note repeated five times faster than the lower. The basic pitch and tempo could be adjusted by means of levers. Cowell composed two works in ...