The terpsitone was an electronic musical instrument

Electronic musical instrument

An electronic musical instrument is a musical instrument that produces its sounds using electronics. Such an instrument sounds by outputting an electrical audio signal that ultimately drives a loudspeaker....

, invented by Léon Theremin

Léon Theremin

Léon Theremin was a Russian and Soviet inventor. He is most famous for his invention of the theremin, one of the first electronic musical instruments. He is also the inventor of interlace, a technique of improving the picture quality of a video signal, widely used in video and television technology...

, which consisted of a platform fitted with space-controlling antennae, through and around which a dancer would control the musical performance. By most accounts, the instrument was nearly impossible to control. Of the three instruments built, only the last one, made by Theremin in 1978 for Lydia Kavina

Lydia Kavina

Lydia Kavina is a Russian theremin player, and is currently the leading performing musician on the instrument.The grandniece of Léon Theremin, Kavina was born in Moscow and began studying the instrument under the direction of Theremin when she was nine years old...

 (his grandniece), survives today. The instrument was named after the Greek muse of dance, Terpsichore

Terpsichore

In Greek mythology, Terpsichore "delight of dancing" was one of the nine Muses, ruling over dance and the dramatic chorus. She lends her name to the word "terpsichorean" which means "of or relating to dance". She is usually depicted sitting down, holding a lyre, accompanying the dancers' choirs...

(from the Greek words τέρπω, "delight", and χoρός, "dance").