Guitar synthesizer

A guitar synthesizer is any one of a number of musical systems that allow a guitarist to access synthesizer capabilities.

[Multi-effects type]
Hammond Innovex Condor GSM (c.1969)

EMS Synthi Hi-Fli (1973) was a very expensive multi-effects.
[F-V converter type]
360 Systems Spectre (mid 1970s) supports the world's first polyphony.

ARP Avatar (c.1977)
is an intermediate result of ARP Centaur VI project.
Starr Labs Z6 Series Ztar