‘Space‐controlled’ elec. instr. developed by the Russian, Lev Theremin (b St Petersburg, 1896; d Moscow, 1993), and first publicly demonstrated in the Soviet Union 1920. Introduced to USA 1927. ‘Space‐controlled’ means that it is played by movts. of the hands, which do not touch the instr. The theremin is built like a radio receiver, with an antenna protruding from the right and a metal loop on the left. The mus. is prod. by 2 high‐frequency circuits, employing oscillating (thermionic) valves, one being at constant frequency while that of the other is altered when the player moves his hand through the air in front of the antenna. The resultant oscillation is called ‘heterodyning’ (‘beating together’), and the heterodyne frequency can be made audible by amplification through a loud‐speaker. Vol. is controlled by a switch and by the movt. of the player's left hand over the metal loop. Sounds similar to the human v. or to those of about 7 instr. can be prod. Plays only one note at a time; range of 5 octaves. First comp. to use instr. was Pashchenko's Symphonic Mystery, for theremin and orch., Leningrad, 1924. Martinů wrote a Fantasy for theremin, str. qt., ob., and pf. Instr. was further developed by Moog and was used by the Beach Boys in ‘hit’ Good Vibrations, 1966.