Léon Theremin Invents an Instrument Played Without Touch

In October 1920, Russian physicist Lev Sergeyevich Termen, known in the West as Leon Theremin, invented an unusual electronic musical instrument while conducting Soviet government-sponsored research into proximity sensors. Originally termed the etherphone or termenvox, the device generated sound without requiring any physical touch from the performer. In 1922 he demonstrated it for Vladimir Lenin at the Kremlin. Following presentations before packed houses across Europe, the inventor took the device to the United States, securing an American patent for the apparatus in 1928.

The instrument relies on two metal antennas that act as capacitive position sensors rather than radio transmitters. Together with the player's hands, each antenna forms a variable capacitor within an internal circuit. One antenna manages volume, while the other governs audio frequency using the heterodyne principle. In this arrangement, two high-frequency radio oscillators beat against each other, with one operating at a steady rate and the other altered by the proximity of the performer's hand. The audible difference between their frequencies is then shaped, amplified, and transmitted to a loudspeaker.