In 1920, a young Soviet physicist named Lev Termen was researching proximity sensors for the Russian government. The Bolsheviks had just won the civil war and Lenin was investing heavily in radio technology — for surveillance, communication, and propaganda. Termen was developing a sensor that would detect when someone approached an antenna. While testing, he noticed the sensor produced a pitch that varied with the position of his hand.

He had accidentally invented the world's first electronic musical instrument.

The theremin — as the West would call it, anglicizing his name — used two antennas. The right hand controlled pitch. The left hand controlled volume. The musician's hands never touched the instrument. Sound came from electromagnetic interference between the player's body and the antennas.

Lenin himself loved it. Termen toured the Soviet Union demonstrating the device. In 1927 he was sent to Germany, France, England, and finally the United States, ostensibly to promote the instrument and earn hard currency. He played it at Carnegie Hall. He demonstrated it to Einstein. He patented it in the US and licensed it to RCA. He married a black ballet dancer in New York at a time when interracial marriage was scandalous.

He was also spying for the NKVD throughout. In 1938 he was suddenly recalled to Moscow, arrested, and imprisoned in a sharashka — a Soviet prison laboratory where engineers worked on classified projects. He invented a key Soviet bug used to listen to the US ambassador's office for seven undetected years.

Released in 1947, he was rehabilitated by Khrushchev and lived to age 97. The theremin became the haunted-house sound effect of mid-century cinema. It is the direct ancestor of every synthesizer.