Invented in 1919 by Leon Theremin, a Russian physicist, and musician, the theremin is the first electronic musical instrument. It's played without touching it at all, other than for making minor adjustments.
The theremin plays one note at a time, and is therefore a monophonic instrument. The sound produced has been compared to sounding like a cross between a stringed instrument in the low to mid registers, and a female voice in the upper range.
For about ten years after it's production by RCA in the late 1920s, the theremin was used mostly for classical style music. For about fifteen to twenty years thereafter, the instrument left the limelight with the acception of performances by noted thereminists like Clara Rockmore, and Samual Hoffman. The instrument made a comback to be heared, but not seen in science fiction, thriller, and horror movies from the late 1940s to the early 1960s.
In the late 1950s, theremins started to reappear as a young electronics enthusiast by the name of Robert A. Moog started producing a small number of theremins with his father.
In the early 1990s, Moog started producing theremins on an industrial scale, and has released several unique versions of theremins sinsce.
Because of the industrial efforts not only by Moog, but producers such as PAIA, Wavefront, Kees, Theremaniacs inc, Thereminplanet, and others, the theremin is making a very strong return to the limelight in all genres of music.
The theremin is now available in many forms, and markets on the web, but is not readily available in local manstream retail markets just yet.