Which electronic instrument did Léon Theremin invent in 1920?

Léon Theremin invented the theremin in 1920.

The theremin is an electronic instrument played without physical contact. A performer moves the hands near two antennas: one controls pitch and the other controls volume. The instrument detects changes in electromagnetic fields created by the player’s hands and converts them into electrical signals.

Theremin demonstrated the instrument in the Soviet Union during the early 1920s. Its eerie, continuously sliding tone later became associated with science-fiction film music, although theremin performers also use it in concert and experimental music.

The theremin is often described as one of the earliest electronic musical instruments played successfully in public. It is not the same as a synthesizer: a synthesizer generally generates and shapes sound through electronic circuits or software, while a traditional theremin uses hand position to control pitch and volume in real time.