Oncor Sound of Salt Lake City sold guitar and bass synthesizers in the 1970s. The Oncor guitar synthesizer had 96 fret switches which determined which note would play when you struck one of the six "strum bars" laid out where you would normally strum the strings. It was a bit like playing a full size Guitar Hero controller

Synthesizer circuitry built into the instrument, let you mute, bend, hammer on, and infinitely sustain notes. The lack of strings however, meant that you couldn't get any real guitar sounds, and the intrument was not a commercial success.