One problem with utilising the heterodyning effect for musical purposes was that as the body came near the vacuum tubes the capacitance of the body caused variations in frequency. Leon Termen realised that[,] rather than being a problem, body capacitance could be used as a control mechanism for an instrument and finally freeing the performer from the keyboard and fixed intonation.Link (via BoingBoing). It also resembles the ooo-eee-ooo screech found in horror movies and "Good Vibrations." I don't know where but she sends me there.
Termen's first machine, built in the [Russia] in 1917[,] was christened the "Theremin" (after himself) or the "Aetherophone" (sound from the 'ether') and was the first instrument to exploit the heterodyning principle. The original Theremin used a foot pedal to control the volume and a switch mechanism to alter the pitch. This prototype evolved into a production model Theremin in 1920[—]this was a unique design, resembling a gramaphone cabinet on 4 legs with a protruding metal antenae and a metal loop. The instrument was played by moving the hands around the metal loop for volume and around the ante[n]nae for pitch. The output was a monophonic continuous tone modulated by the performer. The timbre of the instrument was fixed and resembled a violin string sound.
Indexed by tags music, inventions, electronic, history, theremin.
Image credits: "Lev Sergeivitch Termen playing the 'Theremin,'" courtesy Obsolete.com, borrowed for news-reporting and comment purposes.