Electronic musical instrument like a theramin.
Polyphonic keyboard synthesizer invented 1928 by German acoustician Friedrich Trautwein (1888–1956) and subsequently developed by Oskar Sala as the Mixtur-trautonium. A Neo-Classical Concerto for Trautonium and Strings was composed by Hindemith 1931, and Richard Strauss included the instrument in his Japanese Festival Music 1940.
The instrument remained popular with Hollywood composers until the 1950s.