Ondes Martenot

Ondes Martenot, invented in 1928 by Maurice Martenot, is one of the first electronic musical instruments ever created. It sounds similar to a Theremin, but with more control over the timbre.
Its sound was produced by thermionic valves.
It can be played either via the keyboard or by sliding a metal ring in front of the keyboard and the keys can modulate the pitch of a note up or down by pushing it left or right.
A small drawer on the left contains other controls for the volume and the attack of the note.
Also in this drawer are switches that control the Martenot’s sound. Each switch has its own sound colorand type of wave (sine, tri, etc.) which can be stacked up to create a richer sound.
4 different speakers can be used to modify the sound.
Jonny Greenwood of Radiohead has one in his setup, it was commisioned and built by Analogue Systems which has them for sale for £1050

The French Connection was not born out of nowhere... it was commissioned during 2000 by Jonny Greenwood of the band Radiohead. Greenwood already owned an Ondes Martenot (an instrument built in 1983 by the son of Maurice Martenot) complete with all three resonators, but was nervous about performing with it, fearing that it would be damaged on tour. So he approached Martenot to purchase a second device for live use. Unfortunately for him (but fortunately for the rest of us) his instrument was one of a production run of just 50, and these were long gone - 44 to a music school in Japan, and the remaining five to other musicians.

So Greenwood approached Bob Williams, owner of Analogue Systems, to ask whether he would be prepared to design and build a replica for use with Radiohead's existing RS Integrators. Williams accepted the challenge, and in April 2001 demonstrated a prototype to Greenwood. Following a couple of minor modifications, production began, and the first two French Connections were delivered to Radiohead in May 2001.

more here.