Russian engineer and cellist Leon Theremin (1896–1993) invented one of the earliest electronic instruments that gained wider recognition. The device, originally called Etherophone or Thereminovox, eventually got the name Theremin after its inventor. The first prototype was built in Russia around 1920. Subsequently Theremin tried to get patents for it in Germany and America in 1924 and 1925, and Americans had the first occasion to hear this instrument in the concert in 1927. The Theremin was distinguished by its unearthly sound of monophonic sine waves and the soloing performance technique. However the most distinctive characteristic of the Theremin was that one could play it by simply moving arms near the two antennas.
These features of the Theremin could surprise the majority of viewers, lending the show a high degree of theatricality. Theremin operated on a modulation principle known as a beat frequency oscillation, like many other early electronic music instruments that came later. Two electrical signals of almost equal frequency were mixed. Combining the two gave a third signal that was equal to the difference between the first two frequencies. The remaining tone was the "beat frequency." The radio frequency signal generators used in the Theremin were actually beyond the human hearing range, but the difference between them was audible. The frequency of one of the oscillators was fixed, while the frequency of the other could be varied by moving an object, such as a performer's hand, near a vertical antenna approximately forty-five centimeters high.
When the hand enters the electromagnetic field of this antenna, the oscillator frequency increases, causing the audible beat frequency to change accordingly. The pitch was controlled by moving the hand back and forth in relation to the pitch antenna. In addition to the pitch antenna, there was an additional loop antenna, usually placed horizontally, or a foot pedal to control the sound volume. When the hand comes close to the volume antenna or touch it the sound gets muted. The sound of the Theremin was very close to the sound of a pure sine wave, but with enough sidebands to add depth and fullness to the timbre. It is believed the original Theremin had a range of five octaves. The sound was lasting until the hand was moving in the proximity of the antenna. Special effects like vibrato were easy to create with simple hand movements.
In the 1930s Theremin lived in New York. He spent several productive years there, accepting requests to build various electronic musical instruments. He invented:
- the Rhythmicon, an early form of drum machine. Pressing one of the keys resulted in a rhythm played in certain pitches that could be repeated automatically. Playing multiple notes and rhythms was possible by pressing more than one key at a time. The Rhythmicon was sending light beams onto photoelectric cells to produce electronic frequencies.
- Theremin keyboard was a primitive synthesizer imitating other musical instruments.
- Terpsitone, a dance platform where the movements of a dancer's feet triggered the Theremin's sounds. Terpsitone was also connecting colored light with electronic sounds. The foot-operated instrument was equipped with an array of colored lights mounted behind it. Each light was wired to a different tone pitch.