The theremin (IPA-en???r?m?n), originally known as the aetherphone / etherophone, Thereminophone or termenvox / thereminvox is an early electronic musical instrument controlled without contact from the player. It is named after its Russian inventor, Professor L�on Theremin, who patented the device in 1928. The controlling section usually consists of two metal antennas (antenna (radio)) which sense the position of the players hands and control oscillators (oscillation) for frequency with one hand, and amplitude (volume (volume (sound))) with the other. The electric signals (signal (electrical engineering)) from the theremin are amplified (amplifier) and sent to a loudspeaker.

The theremin is associated with a very eerie (wiktionary:eerie) sound, which has led to its use in movie soundtracks such as those in Spellbound (Spellbound (1945 film)), The Lost Weekend (The Lost Weekend (film)), and The Day the Earth Stood Still (The Day the Earth Stood Still (1951 film)) and as the theme tune for the ITV drama Midsomer Murders. Theremins are also used in art music (especially avant-garde (Experimental music) and 20th- and 21st-century new music) and in popular music genres such as rock (rock music). Psychedelic Rock bands in particular, such as Hawkwind, have often used the theremin in their work.