The theremin is an electronic musical instrument played without physical contact. The performer controls pitch and volume by moving their hands in the space around two antennas, turning gesture, distance, and capacitance into sound.

It is named after its inventor, Leon Theremin, who developed the instrument around 1920 and patented it in 1928. Originally known by names such as etherphone or thereminvox, the theremin became one of the earliest and most iconic electronic musical instruments: a fascinating hybrid of physics, performance, radio-frequency electronics, and musical expression.