The ‘Rhythmicon’ Henry Cowell & Leon Termen. USA, 1930

Henry Cowell and the Rhythmicon
Henry Cowell and the Rhythmicon

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 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.

Rhythmicon Discs
Rhythmicon Discs
After Cowell, the machines were used for psychological research and one example (non working) of the machine survives at the Smithsonian Institute. The Rhythmicon was re-discoverd twenty-five years after its creation by the producer Joe Meek (creator of the innovative hit single ‘Telstar’, 1961) apparently discovered abandoned in a New York pawnbrokers. Meek brought it back to his home studio in London where it was used on several recordings. This Rhythmicon was used to provide music and sound effects for various movies in the Fifties and Sixties, including: ‘The Rains of Ranchipur’; ‘Battle Beneath the Earth’; Powell and Pressburgers’ ‘They’re a Weird Mob’; ‘Dr Strangelove’, and the sixties animated TV series ‘Torchy, The Battery Boy’.The Rhythmicon was also rumoured to have been used on several sixties and seventies records, including: ‘Atom Heart Mother’ by Pink Floyd; ‘The Crazy World of Arthur Brown’ by Arthur Brown, and ‘Robot’ by the Tornadoes. Tangerine Dream also used some sequences from the Rhythmicon on their album ‘Rubicon’.
Rhythmicon Discs
Rhythmicon Discs


“Henry Cowell: A record of his activities” Compiled June 1934 by Olive Thompson Cowell.

12 thoughts on “The ‘Rhythmicon’ Henry Cowell & Leon Termen. USA, 1930”

  1. The first image of Rhythmicon Discs is from a video called ” The Rhythmicon revival after 45 years of silence ” by Andrey Smirnov, who documented his fixing the 3rd version of the original at The Theremin Center, Moscow, in December 2004.

    The tuning of the discs is as follows:
    — foreground: 15 layers progressing in steps of 2 (harmonics 2, 4, 6, …, 30);
    — background: 15 layers progressing in steps of 1 (harmonics 1, 2, 3, …, 15).

    Second set (black disc diagrams) consists of a pitch wheel (left) and tempo wheel (right) which, according to the picture’s source, belonged to the 2nd Rhythmicon built by Lev.

    — left: 16 layers progressing in steps of 6 (harmonics 6, 12, 18, …, 96);
    — right: 16 layers progressing in steps of 1 (harmonics 1, 2, 3, …, 16).

    The choice for having a standard 7-white/5-black piano keyboard as controller is unfortunate, since this irregular layout fails to properly represent the natural harmonic relationships between the rhythmical patterns.

  2. The above comment may produce some misunderstanding. On both images, the disks on the right are responsible for rhythm, and the disks on the left are responsible for pitch. Rhythm disks are almost similar, the only difference – amount of rhythms – 15 and 16. And in the case of these disks it would be better to talk not about harmonics, but rhythms: basic rhythm, rhythm on 2, on 3, on 4, on 5 etc.
    Regarding the pitch disks – all pitched sounds related to harmonics are produced by their means and no other harmonics are available. It means that pitch disk on the first image produces the set of pitches related to the 1st, 2nd, 3rd ,4th etc. up to 15th harmonics by means of layers with 2 holes, 4 holes, 6 holes etc.
    The pitch disk on the second image produces the set of pitches, related to the 1st, 2nd, 3rd etc. up to 16th harmonics by means of layers with 6 holes, 12 holes, 18 holes etc.
    Amount of holes depends only on the range of rotating speeds and required pitch ranges. Slower motor – more holes for the 1st harmonic are required.

  3. This part of the text: “The eventual machine was christened the “Rythmicon”…. etc. is completely wrong. The rhythmicon is not an electronic, but electro-optical rhythm machine, it has nothing in common with the theremin and doesn’t contain any hetrodyning vacuum tube oscillators.

  4. hi. do you have any reliable evidence to back up the Joe Meek story – and all subsequent rumoured uses of the rc in pop music? As far as I know all this is completely untrue. If you have sources to the contrary that would be immensely useful. thanks

  5. I want to make a Rhythmicon VST plugin so I’ve been trying to find out as much as possible about the original instrument to get it as right as possible. The information I need is about the 17th key for “syncopation”. I’ve read that there was an additional beat at a half measure operated by the 17th key. But I can’t see a hole for this in any images I’ve seen and I can’t count up to 17 mirrors for the light path, so I think this info must be incorrect.
    My theory is that the 17th key might be an accent key which maybe increases the total volume when depressed (or maybe mutes it).
    Any insight into this would be greatly appreciated!

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