Guitar synthesizer

This article is about synthesizers or synthesizer controllers that can be played like guitars. For keyboard synthesizers that are held like guitars, see keytar.

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.

Multi-effects type

Hammond Innovex^[b] Condor GSM (c.1969)^[1]

EMS Synthi Hi-Fli (1973) was a very expensive multi-effects.^[2]

F-V converter type

360 Systems Spectre (mid 1970s) supports the world's first polyphony.^[3]

ARP Avatar (c.1977)
is an intermediate result of ARP Centaur VI project. ^[4]

Guitorgan type

VOX V251 Guitar Organ (1966)

Ampeg/Hagstrom's hybrid Swede Patch 2000 (1976) ^[5]

Overview

Today's guitar-synthesizers are direct descendants of originals offered in the 1970s by early manufacturers such as Hammond Innovex & Ovation, Ludwig, Norlin Music/Maestro, 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:

Multi-effects type
Frequency-to-Voltage converter type (using guitar with pickups)
Guitorgan type (using guitar with fretboard switches)

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:

Guitar-synth using guitars: those that are regular electric guitars equipped with special electronic sensors that actuate a synthesizer
Guitar-synth using non-guitar controllers: those that are guitar-like MIDI controllers.

Both types have advantages and disadvantages.

Software solutions

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 strings, and possibly distinguish combination of fret positions and strings) without any special pickups have appeared. See MIDI Guitar ^[6] and Offbeat Guitarist.^[7]

Guitar-based models

Fuji-Roland G303 (1979)^[c] played by Pat Metheny.

Guitar-synthesizers based on electric guitars.

Typical guitar-synths in this category consist of:

an electric guitar or an acoustic guitar;
a hexaphonic pickup (also called a "divided pickup") that provides a separate analog output for each vibrating string;
a converter that converts each of these analog wave forms to corresponding digital representations, from which it recognizes and extracts the fundamental frequency or pitch of each, which it then converts and outputs as electronic (CV/Gate in early days, and later MIDI-formatted) data.

This data can be stored or input directly to a synthesizer that generates corresponding notes that can be made audible when played 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

Roland GK-3 divided pickup mounted on normal electric guitar

Later, Roland developed its GK line of pickups, that could be mounted onto any guitar for use in a guitar-synth system. Based on GK interface, also Roland V-Guitar modeling guitar technology (a kind of DSP effect guitar).

Guitars supporting GK interface

Godin Multiac Jazz.

(right) Gibson Robot Guitar; on version 2, GK interface was introduced.

Several guitar manufacturers, such as Godin, offer guitar models with an integrated "RMC hexaphonic pickup and preamp system" that is compatible with Roland guitar-synth hardware. The RMC pickup system uses a piezo-crystal pickup device built into the saddles of the guitar bridge. This piezo-pickup conducts the vibrations of the strings as a piezo-acoustic signal that can be converted into a (13-pin) hexaphonic synth signal. This setup can be found in the xtSA and the LGX models.^[8]

Fender Musical Instruments released their version of modeling guitar, Fender VG Stratocaster, coined "Roland-ready": a Fender Standard-Series Stratocaster that directly integrates the Roland GK-2 hardware. Note that, although GK hardware is built into the Fender VG Stratocaster, no GK interface is provided. Fender also offered a short-lived American-Series version in the mid-1990s.

MIDI guitars

Casio PG-380 MIDI Guitar (1988)

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.

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 the 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 guitar-synthesizers consist with two separated parts, guitar controller and interface & sound module, where the former control the latter (as in Roland instruments). One of the challenges of using guitar-synthesizers is that not all guitar-playing techniques can be smoothly translated into MIDI and resulting sound. Harmonics, palm mutes, hammer-ons (in which the fretting hand strikes the string onto the fretboard), pull-offs, and pick slides are not easily picked up by guitar-synthesizers, usually due to sloppy fretting hand technique. With the exception of harmonics and palm mutes, these other techniques can be achieved with a concentrated effort to maintain good fretting technique. Similarly, synthesizer part of guitar-synth often lack the variety of controls (sliders, faders, and 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-synthesizers 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. As well, 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 program a sequencer and do MIDI input into digital notation programs such as Sibelius and Finale.

Guitar-like MIDI controllers

Earlier models

SynthAxe (1986) by Bill Aitken

The 1980s-era SynthAxe was a futuristic controller consisting of a fretboard attached to the body at an obtuse angle.^[9] The fretboard strings were used to indicate pitch and sensed string bends. A separate, shorter set of strings were used for picking and strumming. These triggered the notes fretted on the fretboard's strings. It also featured trigger keys that could be used instead of the trigger strings. A whammy bar was assignable to any MIDI parameter. The SynthAxe was prohibitively expensive and therefore not widely used. Two of the most famous SynthAxe users are guitarist Allan Holdsworth and percussionist Roy "Futureman" Wooten of the jazz quartet Béla Fleck and the Flecktones. Wooten has programmed his modified SynthAxe controller with a variety of Drum Kit and Percussion sounds, using his fingers to tap out complex polyrhythmic beats and grooves, playing the part of a "virtual drummer" in the band on his customized SynthAxe-based Drumitar, especially in the band's early years. In more recent years he has switched between his Drumitar and a more traditional drum kit. Futureman's custom Drumitar was modified from a SynthAxe previously owned by jazz guitarist Lee Ritenour.

Yamaha originally entered the market with a guitar-like MIDI controller called the "G-10". It was considerably less expensive than the SynthAxe. The G-10 had two assignable knobs and an assignable whammy bar and it used six strings, all the same gauge [thickness], which sensed both right- and left-hand input. The fact that the strings were all of the same thickness made the instrument feel substantially different for a player, in contrast to the typical guitar, and may have hindered the instrument's acceptance. Both the SynthAxe and Yamaha G-10 have been discontinued.

Recent models

Yamaha EG-AG

Starr Labs Ztar played by Rob Swire

You Rock Guitar (MIDI guitar controller and synth)

Beginning in the early 2000s, Yamaha have re-entered the market with simple midi guitars (EZ-AG and EZ-EG) these have illuminated frets to teach finger technique and 20 voices.

Starr Labs' Ztar is one of the few remaining guitar-like controller product lines still in production. A Ztar differs significantly from the SynthAxe and Yamaha G-10 in that the "fretboard" is covered with keys, not strings. Keys in the same row can trigger notes at the same time. This has no analog on a real guitar. It would be as if a single string were polyphonic. A number of variations are available, including an instrument that uses strings for strumming or picking, to trigger notes, whereas the pitch of the notes is determined by the keys that cover what would be a "fretboard" in an ordinary, stringed guitar. Starr labs recently introduced the Z5S, a simpler and less expensive version of the Z6S. MIDI guitar controllers have regained popularity due to the Z6 model, possibly because of its usage by Rob Swire of Pendulum, who uses it on songs where he is required to perform vocals.

The You Rock Guitar, introduced in 2010 by You Rock Digital, combines a MIDI guitar controller/recorder with a patented touch-sensitive fingerboard and an on-board synthesizer. The instrument supports not only strumming and picking, but also tapping and sliding techniques, and provides a whammy bar for pitch bending and a modulation. Control panel software gives users control over 40 parameters, including velocity tables, string sensitivity, and synthesizer presets. The You Rock Guitar is used by guitarists such as George Pajon Jr. (Fergie, The Black Eyed Peas) and Josh Kelley.

Video game guitar controllers

Fender Mustang Pro Guitar Controller

Squier Stratocaster Pro Controller

Rock Band 3 features three guitar controllers.

One is modeled after the Fender Mustang, with 6 string sensors stretching from the bridge to the location of the neck pickup of a standard guitar and 102 buttons in 6 columns of 17 frets, which together create MIDI note data. The other is being built with Fender and is a fully functional guitar, with a bridge pickup "listening" to the strings and sending MIDI information to the MIDI port. The Mustang model will retail at 150 USD.

"You Rock Guitar" is compatible with Guitar Hero and Rock Band 3, including RB 3 Pro Mode. It was named Innovation of the Year by USA Today in 2010. The guitar provides a number of features that help gamers to become guitarists. The You Rock Practice Mode provides audible feedback when the user plays with the guitar's built-in song loops. The guitar can simultaneously drive a game system, an amplifier, headphones, a MIDI synthesizer, and music software via USB. The street price is around $200.

Software guitar controllers

A+ MIDI Guitar & GarageBand setup (2011) by WKode

In March 2011, WKode released the first true software MIDI guitar controller for the iPhone and iPod Touch. Since it is an iOS app, it is affordably accessible to anyone with an iPhone or iPod Touch. It works with any music creation programs like GarageBand, Logic, Reason, Kore, Kontakt, Ableton Live, etc. that accepts MIDI input via the open-sourced DSMidiWifi Server maintained by Google Code. Setup is easy; all you need is a computer and a Wi-Fi router.

Another example is the Misa Digital Guitar, which is really another guitar shaped MIDI controller that includes a minimalistic touchscreen interface at the guitar's body (similar to the Korg Kaoss Pad) and 24 touch sensitive frets, with configurability at the sound module end. The Misa digital guitar software is open source, and powered by the Linux operating system. This MIDI device includes Ethernet (and SSH server) and is produced by Misa Digital which is based in Sydney, Australia.

Pros and cons

The advantages of the guitar-like MIDI controller systems are that the tracking [the speed and accuracy of the notes the instrument produces] is much better than guitar-based systems, which means that there is no noticeable latency or pitch glitches. As well, whammy bars and other controllers can be assigned to any MIDI function, which gives the performer more on-stage control of their sound. Further, these controllers offer playing options, such as the keyboard-like tapping style, that are not possible on traditional guitars. Finally, the instruments with touch-sensitive fingerboards never need tuning, and they are easier on the fingers of beginning and casual players.

The disadvantages for guitar players are that the controller is not exactly a guitar, and the feel is different. Some instruments are rare and expensive, which may make it difficult to repair or service them.

Guitar sound synthesis

	D-GTS Guitar fret = 440Hz
Problems playing this file? See media help.

With the aid of faster computers it has been possible to synthesize very realistic guitar sounds. Some examples of guitar-like sound synthesis include StringStudio of Applied Acoustics Systems, and VB-1 of Steinberg. Many of these follow the convention of using physical modeling, where the physics of playing a guitar are simulated. This is usually done in real-time to allow for live performance. The Karplus-Strong string synthesis algorithm is one such method for guitar-like sound generation through physical modeling. Since this only models the vibrations of strings additional effects are needed to simulate all sounds possible from playing a physical guitar. An example of the sound synthesizer D - GTS below illustrates modeling both the strings and the fretboard of a guitar. See Physical modelling synthesis for more information.