An electronic music instrument which precedes the development of the synthesizer. The basic circuitry was devised by Russian expat Leon Theremin in 1920 (or 1919; sources disagree). The instrument caused a sensation at the time it was introduced, and Theremin received a job offer from RCA to develop a commercial version. However, the Great Depression killed the mass market, and the instrument has been somewhat of a specialst item ever since. Jimmy Page uses a Theremin in Led Zeppelin's Whole Lotta Love