A pioneering electronic music instrument, created by the RCA corporation in the 1950s. There were actually two units built. The original one was built and installed at RCA's Sarnoff Research Center in Princeton, New Jersey USA in 1955. Several prominent avant-garde musicians of the day contributed conceptual ideas to the design, including Vladimir Ussachevsky, but the actual electrical engineering was executed by RCA engineers Herbert Belar and Harry Olson. This was a two-voice polyphonic system, using multiple frequency sources with octave divider circuits to produce the notes of the musical scale. To modify the timbre, it had high pass and low pass filters for each voice, as well as resonators, fixed filters, and reverberation devices that could be patched in. The circuitry was executed