The ondes Martenot (/ˈoʊnd mɑːrtᵻˈnoʊ/ or OHND mar-tə-NOH; French: [ɔ̃d maʁtəno], "Martenot waves"), also known as the ondium Martenot, Martenot and ondes musicales, is an early electronic musical instrument invented in 1928 by 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.