An early electronic musical instrument invented in 1928 by Frenchman Maurice Martenot. The original design was similar in sound to the theremin. The sonic capabilities of the instrument were later expanded by the addition of timbral controls and switchable loudspeakers.

The instrument's eerie wavering notes are produced by varying the frequency of oscillation in vacuum tubes. The production of the instrument stopped in 1988, but several conservatories in France still teach it.