Roland GR-300
The Roland GR-300 is an analog guitar synthesizer manufactured by Roland Corporation. It was introduced to market in 1980.
The GR-300 was considered the first "playable" guitar synthesizer.. The GR-300 had no MIDI and could initially only be played/controlled with a Roland G series guitar controller.
The synthesizer used internal circuitry to convert the guitar's pitch to a control voltage that would then be able to determine the pitch of the VCOs and trigger the envelope-controlled VCF, if enabled. This process required a hexaphonic pickup to be installed on the guitar, essentially sending 6 separate signals, one for each string on the guitar, to individual pitch-to-voltage conversion circuits in the synthesizer module.
The actual synthesizer module sat on the floor and had the rugged appearance of a large, bright blue guitar-type foot pedal and did not resemble an actual keyboard synthesizer at all. It featured six-voice polyphony, one voice per string and two oscillators per voice. Each pair of VCOs were harmonically locked to each string but could be tuned separately to play different pitches. The GR-300 also featured a VCF with variable length sweep up and down, and an LFO to add pitch vibrato to the oscillators. Each string had an enable-disable switch as well as a string sensitivity switch. Built-in footswitches controlled the VCO mode, the VCO harmonize pitch, and the VCF mode. There was also an expression pedal control input for the cutoff frequency of the VCF. It did not have any patch memory, other than the ability to pre-set pitches of the tunable oscillator with Pitch A/B footswitches - which could be set to latching or momentary. The GR-300 could output either the guitar, the synth, or a mix of the two.