Ondist

Ondes Martenot
An ondes Martenot (seventh generation model, 1975)
Dates	1928–present
Technical specifications
Polyphony	none
Oscillator	vacuum tube
Synthesis type	heterodyne
Input/output
Keyboard	1 or 2 x 35 note manuals (G2–F5)

The ondes Martenot (/ˈoʊndmɑːrtəˈnoʊ/ 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.

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 offer instruction to students of the instrument.

In 1997 the Ondéa project began designing an instrument based on the ondes Martenot. Since the Martenot name is still protected, the new instrument is called Ondéa, but has the playing and operational characteristics of the original ondes Martenot. In 2001 a completed prototype was first used in concerts. These instruments have been in regular use since 2005. In 2017, a new version of the Ondéa, built by Audities Studio of Calgary, Alberta, Canada, became available.

Since 2008 Jean-Loup Dierstein, with the support of Maurice Martenot's son, has been developing a new, officially named ondes Musicales instrument based on the model used when production stopped in 1988.