Radio engineers experimenting with radio vacuum tubes discovered the principles of beat frequency or heterodyning oscillators by chance during the first decades of the twentieth century. The heterodyning effect is created by two high radio frequency sound waves of similar but varying frequency combining and creating a lower audible frequency, equal to the difference between the two radio frequencies. The musical potential of the effect was noted by several engineers and designers including Maurice Martenot, Nikolay Obukhov, Armand Givelet and Leon (or Lev) Sergeivitch Thermen the Russian Cellist and electronic engineer.
One problem with utilizing the heterodyning effect for musical purposes was that as the body came near the vacuum tubes the capacitance of the body caused variations in frequency. Leon Thermen realized that rather than being a problem, body capacitance could be used as a control mechanism for an instrument and finally freeing the performer from the keyboard and fixed intonation.
Termen's first machine (shown above), built in the USSR in 1917 was christened the "Theremin" (after himself) and was the first instrument to make use of the heterodyning principle. The original Theremin used a foot pedal to control the volume and a switch mechanism to alter the pitch. This prototype evolved into a production model Theremin in 1920, this was a unique design, resembling a gramophone cabinet on 4 legs with a protruding metal antennae and a metal loop. The instrument was played by moving the hands around the metal loop for volume and around the antennae for pitch. The output was a monophonic continuous tone controlled by the performer. The resonance of the instrument was fixed and resembled a violin string sound. The sound was produced directly by the heterodyning combination of two radio-frequency oscillators: one operating at a fixed frequency of 170,000 Hz, the other with a variable frequency between 168,000 and 170,000 Hz. The frequency of the second oscillator being governed by the closeness of the musician's hand to the pitch antenna.
This Theremin model was first shown to the public at the Moscow Industrial Fair in 1920 and was witnessed by Lenin who requested lessons on the instrument. Lenin later commissioned 600 models of the Theremin to be built and toured around the Soviet Union.
An early version of the Ondes-Martenot
Maurice Martenot a Cellist and radio Telegraphist, met the Russian designer of the Theremin, Leon Termen in 1923, this meeting lead him to design an instrument based on Termen’s ideas, the first model, the "Ondes-Martenot" was patented on the 2nd of April 1928 under the name "Perfectionnements aux instruments de musique électriques" (improvements to electronic music instruments).
A concert version of the Ondes-Martenot
His aim was to produce a versatile electronic instrument that was immediately familiar to orchestral musicians. The first versions looked nothing like the later production models: consisting of two table-mounted units controlled by a performer who manipulated a string attached to a finger ring. This device was later incorporated as a fingerboard strip above the keyboard. Later versions used a standard
The Ondes-Martenot became the first successful electronic instrument and the only one of its generation that is still used by orchestras today. Maurice Martenot himself became, 20 years after its invention, a professor at the Paris Conservatoire teaching lessons in the Ondes-Martenot.
Termen left the Soviet Union in 1927 for the United States where he was granted a patent for the Theremin in 1928. The Theremin was marketed and distributed in the USA by RCA during the 1930's and continues, in a transistorized form, to be manufactured by Robert Moog's ‘Big Briar’ company.
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