A guitar synthesizer (also guitar synth, alternatively guitar-synthesizer, guitar-synth, guitar/synthesizer, guitar/synth, g-synth or synth guitar) is any one of a number of musical instrument systems that allow a guitar player to play synthesizer sound.
Today's guitar-synthesizers are direct descendants of originals offered in the 1970s by early manufacturers such as Hammond Innovex & Ovation, Ludwig, Norlin Music/, EMS, 360 Systems, Ampeg & Hagström, Arp, Roland Corporation & FujiGen, Electro-Harmonix. Other notable manufacturers include New England Digital, Terratec/Axon, Starr Labs, Ibanez, Casio, Holt Electro Acoustic Research, Zeta Systems, and Yamaha.
In the early days, there were three main types of guitar-synthesizers:
Later, multi-effects type evolved into modeling guitar, and the other two types evolved into current guitar-synthesizers.
And today, there are two main types of guitar-synthesizers:
Both types have advantages and disadvantages.
Note that although the term "MIDI guitar" is sometimes used as a synonym, MIDI is not the indispensable feature of guitar-synthesizers, especially after the great advances in the DSP technology. For example, recently, software guitar-synthesizers featuring polyphonic audio recognition (recognizing polyphonic pitches of each string, and possibly distinguish combination of fret positions and strings) without any special pickups have appeared. See MIDI Guitar and Offbeat Guitarist.