In 1955 Harry Olson and Belar, both working for RCA, invented the Electronic Music Synthesizer
(aka the Olson-Belar Sound Synthesizer). This synth used sawtooth waves that were filtered for other types of timbres. (It is rumored to have been built for the artificial creation of human speech) This synth became the RCA Electronic Music Synthesizer Mark I.
The RCA Mark I has 12 fixed tuning-fork-based oscillators in equal temperment, whose frequency could be divided down to produce different octaves. Originally, tracks were recorded onto disc (up to six at once, replayed by six styli!. The whole thing took up seven tall 19" racks.