G303 (1979) played by
Pat Metheny. Typical instruments in this category consist of: • an
electric,
acoustic or
bass guitar; • a
hexaphonic pickup (also called a "divided pickup") that provides a separate analog output for each vibrating string; • a
converter that
translates each of these analog signals to corresponding digital representations, extracting the
fundamental frequency or
pitch of each, and passing this data along (
CV/Gate in early days, and later
MIDI-formatted). This digital output can be stored or input directly to a synthesizer that generates corresponding
notes made audible through an amplifier and speaker. These components may be integrated into the instrument body or modularized in different ways. The hexaphonic pickup may be a separate component added to the guitar, or it may be built-in. Earlier guitar-synths required the musician to use a proprietary guitar with an integrated hexaphonic pickup.
Roland GK interface GS-500 controller for its GR-500 guitar synthesizer (1977). --> Roland developed its GK series of hexaphonic drivers, consisting of a divided pickup and associated electronics (essentially a buffer preamp for each string signal). These were used in two ways, either with pickup and buffer module mountable to the guitar, or as a "GK-KIT" intended to be fitted into a guitar body by a luthier or manufacturer. The initial GK-1 had 24 output pins, with a resultantly bulky interface cable. The design evolved into a smaller 13-pin format, used in the GK-2, GK-2A, and GK-3 pickups, as well as the GK-3B bass pickup. Guitar manufacturers that offered models with the installed "Roland-ready" pickup kit include Switch Music,
Washburn,
Fender,
Squier, and
Ibanez (RG420GK).
Fender released their
Fender VG Stratocaster, a Standard Series instrument with inbuilt GK-2A hexaphonic pickup kit. Fender had previously offered a short-lived American Series version in the mid-1990s.
Godin and a few other guitar manufacturers have offered guitar models with an integrated "RMC hexaphonic pickup and preamp system" that is compatible with Roland devices. The RMC system uses
piezo-crystal pickups built into the saddles of the guitar bridge, which conduct the vibrations of the strings as a signal that can be converted into a (13-pin) hexaphonic synth signal. This setup can be found in the xtSA and the LGX models. The GK drivers or compatible controllers are connected to a dedicated synthesizer module like
Roland GR-1 or Roland GR-55 via a cable with 13-pin connectors. The module sits on the floor and has the appearance of a large
effects unit, with footswitches for the selection of sounds and memory banks.
MIDI guitars Usually, a cable connects the hexaphonic pickup to the converter. This allows the guitarist to be unencumbered by an on-board converter. However, several
Casio models in the PG and MG product lines integrated the guitar, the hex pickup, and the converter as a single unit. Casio remains the only manufacturer to try this approach. The advantage of this arrangement is that a MIDI cable can be plugged directly into the guitar. Disadvantages include weight and the need for an external power supply. In addition to these configurations, the converter may also be combined with a synthesizer. The earliest models were combination converter/synthesizers, and this type is still produced. As the early integrated models predated the MIDI standard, their components were not interchangeable; the guitarist's only option was to use whatever synthesizer came with the converter, and vice versa. By the 2000s (decade), however, all converter/synthesizers were MIDI-compatible, so any synthesizer with MIDI-input capability (the vast majority since the 1990s) can be used. Stand-alone converter units also drive synthesizers via MIDI.
Pros and cons Among the advantages of synth guitars are that the musician can play either the guitar or the synthesizer alone, or blend the
timbres of both together in any ratio. Many models can be used with almost any guitar, with the addition of a hexaphonic pickup. In the early systems, there was a detectable latency, especially at lower pitches, between playing a note on the guitar and the note's sounding on the synthesizer, but this was remedied in 2000s-era instruments. While this type is also somewhat prone to note-tracking glitches, the problem can be overcome by adjusting the sensitivity controls of the pickup or converter—and by playing more precisely. Another possible disadvantage is that not all of the variable performance parameters available on a synthesizer can be actuated from a guitar; a synth guitar lacks assignable controls to open a filter in real-time, for example. Nevertheless, contemporary synth-guitar designs often include an
expression pedal for such purposes.
Translation of guitar techniques Some systems consist of two separated parts, the
guitar controller and the
interface and sound module, where the former controls the latter (as in Roland instruments). One of the challenges of guitar synths is that not all performance techniques can be smoothly translated into
MIDI and resulting sound.
Harmonics,
palm mutes,
hammer-ons and
pull-offs, and
pick slides are not easily picked up by guitar synths, largely due to imperfect fretting technique; with the exception of harmonics and palm mutes, these techniques can be achieved with a concentrated effort to maintain good fretting. Similarly, the synthesizer portion of a system often lacks the variety of controls (sliders, faders, knobs) for synthesis parameters that are normally available on a standard keyboard synthesizer. Nevertheless, controlling a synthesizer with a guitar has some advantages over a keyboard. More expansive chords are possible, and some intervals are easier to reach. As well, guitar synths provide access to sounds normally available only to keyboard players and percussionists. A guitar player could play a
flute part using a sampled flute patch, or play
percussion by triggering synth drum voices. By blending the regular electric guitar tone with synthesized sounds, a guitarist can create a hybrid timbre. The guitar synth also enables a guitarist with limited or no keyboard-playing skills to provide MIDI input into digital
notation programs such as
Sibelius,
Finale or
MuseScore. == Guitar-like MIDI controllers ==