Guitar synthesizers use guitar sounds to trigger synthesizer patches. Some older guitar sythns used buttons on a mock fretboard to trigger sounds directly, but most synthesizers use some kind of pitch-to-data conversion. This data conversion can take place within the body of the guitar, or with an externally mounted pickup. Roland guitar synths use a GK3 pickup to the conversion, and then a special jack to transfer the data into the synthesizer module. Other pickups may convert the data directly into MIDI data. The data transfers out through a MIDI cable or USB.
Some guitar effects have a converter built in. These convert the guitar signal to data triggers rather than picking up directly from the guitar.
Because of the inherent analog to digital conversion, and the time necessary to trigger synthesizer sounds, some lag occurs between picking the note and the sound produced. Guitar synth players learn to play slightly ahead of the beat to compensate. Latency is longer with lower pitched notes. Choosing synth patches that do not have a sharp attack can minimize the effect of the latency. Also, layering in the guitar sound from the magnetic pickups can help.
The data transfer is imperfect, and synthesizer patches were designed from the simpler process of just pressing a keyboard key down. Glitches and unexpected notes are common with guitar synthesizers. Just like any technique, practice and adjusting technique to fit the medium are required.
The guitar synth can play any synthesizer patch, but that does not mean any player automatically sounds like Rick Wakeman just by plugging the in synth. Techniques effective for the guitar synth may be different than traditional keyboard synth sounds.
As mentioned above, layering in the magnetic or piezo pickups from a guitar can hide glitches, latency, and inconsistency. Generally, the synth should be used judiciously, like any technique.
Playing a layered sound with the main playing being on the magnetic pickups and the synth just paying a background pad is quite effective. Set the synth to strings or some ambient pad and mix it in low, and the synth will just add to the color of a sound like an advanced form of reverb.
Setting the synth to a bass patch and doubling the guitar is also effective. A line like “Black Dog” by Led Zeppelin might be hard to teach to a bass player, but the synth pays it automatically.
Using a sustain pedal or choosing sounds with a long decay time can also help hide glitches. A standard piano sound is tough to pull off without a lot of practice.
Stringed ethnic instruments like sitar and banjo work well with the synth because of the similarities in playing style.
Trying to emulate an acoustic instrument is usually a mistake. People know what a saxophone is supposed to sound like, and trying to imitate an expert player is quite difficult. Instead, use electronic sounds that derive from synthesizer settings. The audience has fewer expectations about what the sound is supposed to be, so they are more open to these patches.
Synthesizer patches based on guitar sounds are usually unsatisfying because they do not sound as good as a real guitar. However, layering in a guitar patch can fill out a sound. Mix the synth low in the mix. Adding a 12-string patch to a sound can make an electric guitar sound more like an acoustic.
Lead type synth patches work well for solos. Audiences are more open to different sounds on solo lines because of the tradition of guitar players experimenting with timbres during solos.
Synth settings are a godsend to the solo artist that does a lot of looping. Percussion, bass, pads, and keys are all options for the looping process.
Audience reaction to synthesizers can be mixed. When people hear electronics used in a live situation, they tend to believe the hardware is doing all the work and the player is cheating. Actually, the exact opposite is true. Learning to play with technology is a difficult, learned process.
Initial reaction to the novelty of the synthesizer will be positive. People who have never heard synthesizer sounds coming from a guitar are intrigued. However, overuse of the technology can lead to annoyance. Just like any technique, do not overuse the synth.