I have often wondered while listening to Radiohead’s Kid A, about the strange sounds one gets to hear.A rudimentary google search told me that the instrument is called Ondes Martenot.
Ondes Martenot means “Martenot’s waves” and is pronounced “OWNED MARTENO”, is a early electronic music instrument. It was first built in 1928 by Maurice Martenot. According to Guardian “he was fascinated by the accidental overlaps of tones from military radio oscillators — which he found musical — and wondered if he could develop an instrument that could replicate them, but with the same tonal expression of his beloved cello.” 
The early electronic instruments had some eerie thing about them. For instance Theremin is still a very peculiar device, even after decades, since it has first appeared. Ondes Martenot is a close cousin of Theremin, but much more acceptable in appearance. Theremin is played without touching the instrument, by changing the electromagnetic field by the movement of the player’s hands. Ondes Martenot is much more conventional, in the sense it has a key board and ring like contraption to play it.
The early electronic instruments had some eerie thing about them. For instance Theremin is still a very peculiar device, even after decades, since it has first appeared. Ondes Martenot is a close cousin of Theremin, but much more acceptable in appearance. Theremin is played without touching the instrument, by changing the electromagnetic field by the movement of the player’s hands. Ondes Martenot is much more conventional, in the sense it has a key board and ring like contraption to play it.If you have tuned an old Murphy radio, you might have heard that sound that it makes while searching for stations. Ondes Martenot is capable of creating the same sound, which is incidently the sound made by Theremin as well. These old radios and Ondes Martenot work on the same principle, vacuum tubes. Ondes Martenot uses a ring to create this sound. The ring slides over a string and can be moved from one end to
another to achieve levels of pitches. Ondes Martenot is capable for producing an entire range of sounds from flute to bassoon. It can even create sounds of strings and percussion instruments. The instrument also has a keyboard, one interesting feature is that the keys of Ondes Martenot can vibrate, Martenot was originally Cello player and Ondes Martenot has inherited this feature from it’s creator’s favorite instrument.
Ondes Martenot has been used in soundtracks of movies, especially sci-fi and horror ones. The staple background score used in many of these movies are from Ondes Martenot. There is a theory that Ondes Martenot is used in the Star Trek theme, but that is a lie! In popular music, Radiohead albums like Kid A, Amnesiac, Hail to the theif and In rainbows have Ondes Martenot sounds in copious quantities.
Jonny Greenwood of Radiohead had Olivier Messiaen for a childhood hero, it was Messiaen who first used Ondes Martenot in a classical musical piece. Give a listen to the song “Kid A” from the Radiohead album of the same name or “How to dissappear completely from the same album and tune your ears for Ondes Martenot. I believe Greenwood has used the instrument to terrific effect in this album. But before doing that I suggest you to watch this video to get a feel of the instrument,the speaker is Jean Laurendeau an exponent of Ondes Martenot.
Check out this Scotch Mist version of Jigsaw Falling into place, you can see Greenwood using Ondes Martenot.
