In 1916 the American Avant-Garde composer Henry Cowell was working with ideas of controlling cross rhythms and tonal sequences with a keyboard, he wrote several quartet type pieces that used combinations of rhythms and overtones that were not possible to play apart from using some kind of mechanical control- “un-performable by any known human agency and I thought of them as purely fanciful”.(Henry Cowell) In 1930 Cowell introduced his idea to Leon Termen, the inventor of the Theremin, and commissioned him to build him a machine capable of transforming harmonic data into rhythmic data and vice versa.
“My part in its invention was to invent the idea that such a rhythmic instrument was a necessity to further rhythmic development, which has reached a limit more or less, in performance by hand, an needed the application of mechanical aid. The which the instrument was to accomplish and what rhythms it should do and the pitch it should have and the relation between the pitch and rhythms are my ideas. I also conceived that the principle of broken up light playing on a photo-electric cell would be the best means of making it practical. With this idea I went to Theremin who did the rest – he invented the method by which the light would be cut, did the electrical calculations and built the instrument.”Henry Cowell
“The rhythmic control possible in playing and imparting exactitudes in cross rhythms are bewildering to contemplate and the potentialities of the instrument should be multifarious… Mr. Cowell used his rythmicon to accompany a set of violin movements which he had written for the occasion…. The accompaniment was a strange complexity of rhythmical interweavings and cross currents of a cunning and precision as never before fell on the ears of man and the sound pattern was as uncanny as the motion… The write believes that the pure genius of Henry Cowell has put forward a principle which will strongly influence the face of all future music.”Homer Henly, May 20, 1932
The eventual machine was christened the “Rythmicon” or “Polyrhythmophone” and was the first electronic rhythm machine. The Rhythmicon was a keyboard instrument based on the Theremin, using the same type of sound generation – hetrodyning vacuum tube oscillators. The 17 key polyphonic keyboard produced a single note repeated in periodic rhythm for as long as it was held down, the rhythmic content being generated from rotating disks interrupting light beams that triggered photo-electric cells. The 17th key of the keyboard added an extra beat in the middle of each bar. The transposable keyboard was tuned to an unusual pitch based on the rhythmic speed of the sequences and the basic pitch and tempo could be adjusted by means of levers.Cowell wrote two works for the Rythmicon “Rythmicana” and “Music for Violin and Rythmicon” (a computer simulation of this work was reproduced in 1972). Cowell lost interest in the machine, transferring his interest to ethnic music and the machine was mothballed.