The Clavivox was a keyboard sound synthesizer and sequencer developed by American composer Raymond Scott beginning in 1950. He was granted a US patent for it on Feb. 3, 1959. (U.S. Patent 2,871,745)
Scott had earlier built a theremin as a toy for his daughter Carrie. In his first Clavivox prototype, he used a theremin module built by a young Bob Moog (who was more than 25 years younger than Scott). The unit allowed the use of portamento over a 3-octave range. Scott then added amplitude envelopes, vibrato and other effects to the Clavivox.
"A lot of the sound-producing circuitry of the Clavivox resembled very closely the first analog synthesizer my company made in the mid-'60s," Moog explained years later. "Some of the sounds are not the same, but they're close."