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History of the Guitar Synthesiser

A personal account of its development

A personal look at designs past and present


Ever since the inception of the electric guitar, musicians and manufacturers have been working to extend the range of sounds available from this popular and versatile instrument.

The first significant step was probably the original fuzz box, or tone bender as it was then called, which was invented by an electro-musician called Garry Hurst in the mid-sixties. This was basically an overdriven preamp which produced a harsh clipped sound, unlike the more subtle distortion unit currently available and was used to great effect by such notables as Jeff Beck, then with the Yardbirds and also the legendary Spencer Davies Group on several of their hit singles, including "Keep on Running".

The first time I heard this exciting new sound was on the Stones single "Satisfaction" and I remember trying to design a device to produce the same sound. As I was still at school, my expertise was not what it might have been, but putting two home built Hawaiian guitar preamps in series provided a passable imitation.

Soon to follow was the Wah Wah Pedal from Vox which was duly played to death as seems to be the fate of most new musical toys. The Wah Wah pedal was really the forerunner of the synthesiser filter, although it had a fixed Q and was resistor controlled, not voltage controlled.

Strangely, even before this time, the ever-enterprising Vox team was producing the Organ guitar, which was basically a modified Vox Phantom that looked rather like a Victory V tablet with a neck on it. This consisted of six resistor controlled oscillators, one for each string, and metal inserts set into its plastic frets to make electrical contact with the strings when fretted. This meant that holding down any string produced a sound, with no help at all needed from the right hand, and of course, open strings did not play.

Due to the difficulties of playing a one handed guitar, this machine never really caught on, but the idea was very innovative for its time.

EMS Hi Fli synth.

After signal processing had run the gamut of echo, reverb, flanging, phasing, fuzz and wah wah, various firms decided to attempt the production of a proper guitar synthesiser as the lucky keyboard player was galloping years ahead, with programmable polyphonic synths and a whole host of other electronic keyboard instruments, whilst the poor guitarist was still cursing the crackling pot in his Wah Wah pedal in efforts to copy the sound of Wailing Jim H, one of the more accomplished users.

Around the mid-seventies, after the appearance of the EMS Hi Fli synth, which was really a box of conventional effects, several guitar synths appeared at once during an otherwise ordinary music trade fair. There were several notable differences in approach to the problem by different manufacturers. Hagstrom produced a guitar/synthesiser interface using a specially modified Hagstrom guitar. This, like the Vox organ guitar, used wired frets but the technology was all up to date, including digital scanning of the fingerboard. The player/instrument relationship was rather cumbersome, however, as the guitar was, I believe, still a left hand only job like the old Vox.

Arp Avatar guitar synth.


ARP Avatar



ARP were showing the Avatar, which consisted of a hexaphonic pickup fed via a special lead into a modified Odyssey synthesiser. There was a last note priority system to make sure that only one string at a time was processed and a pitch to voltage converter which produced the control voltage for the Odyssey. This sounded so impressive that I soon acquired my own instrument.

The shortcomings of such a machine soon became very obvious, the most annoying being the machine's tendency to yodel when one's picking technique was anything other than slow and meticulous (and sometimes even then). This was due to the pitch to voltage converter's inability to accurately track the pitch of the guitar string with its many harmonics and also its inability to lock onto the pitch when the string vibrations were dying away causing all the notes to end with a grunching sound reminiscent of someone trying to play chords through an octave divider. The synth had polyphonic fuzz guitar but was really a monophonic device. I took it back to the shop at the end of the week and swapped it for the Roland GR500; this seemed more interesting as it had polyphonic features.

Korg X-911



Another monophonic device, Korg's preset design introduced some time later was also suitable for use with a trumpet, saxophone or other instrument. Two sets of tabs referred to imitative sounds — Electric Bass, Tuba, Distortion Guitar, Violin and Flute — or Synth sounds in various footages and waveshapes. Portamento, Balance, Interval and Wah controls together with combineable presets made the X-911 quite versatile, offering "2047 different tone colour combinations", but even this couldn't compensate for the lack of polyphony.

Roland GR500/Transcendent 2000 system.


Roland GR500



This was described by the makers as Paraphonic, rather than polyphonic, and had several very interesting features including infinite sustain. The label Paraphonic came about because the guitar synth had four different sound producing sections, which would be played simultaneously as well as the conventional guitar sound, although only two of these sections offered any sort of polyphonic capability. The four sections were as follows:

Polyphonic — which consisted of a processed versions of the sound produced by the guitar strings, then fed through a four band graphic and a simple three parameter envelope shaper. Infinite sustain was possible on this and all other sections except straight guitar.

Bass — which was monophonic and divided directly from the string pitch with percussive attack to simulate picking if required. An ADS envelope was also provided.

Solo melody — a monophonic synth with envelope and filter controls to which could be added the output of the polyphonic section to produce polyphonic filtered effects. Portamento was available, but no pitch vibrato was provided (although electronically a simple change could provide it).

External synth — this was an output to drive a conventional one volt per octave analogue synth and greatly enhances the overall sound, especially when vibrato is added to the external synth, which in my case was a Transcendent 2000 with a vibrato depth pedal fitted.

The guitar and synth must be used together as the guitar contains quite a lot of electronics, including the hex pick up preamps, section select and volume controls and the mysterious infinite sustain.

The principle of the infinite sustain is very simple. When a string is fretted and plucked with sufficient force to exceed the picking threshold, a current-buffered version of the string output is fed into the string at the bridge end (hence the plastic bridge saddles) and along to the frets which are all electrically common. This in itself would not do anything dramatic, but the strong magnet concealed behind the plastic dummy pickup invokes one of Faraday's Laws (the same one that applies to motors) and the string is then obliged to keep oscillating, albeit at a very low level.

This means that the normal guitar sound can decay to this low volume, whilst the sensitive hexaphonic pickup can still detect the vibrations in order to drive the synth indefinitely or until you get cramp in your hand. This facility does not operate on open strings where the decay lasts about twenty seconds.

The overall instrument is probably best described as the guitarist's answer to the ARP Omni, but there are many regions where the guitar synth and keyboard synth do not overlap. Because the pitch converter takes a finite time to extract the necessary pitch information, sounds with a sharp percussive attack sound unconvincing. Similarly, the circuitry does not know when you are going to stop playing and so it is not possible to set a release time to extend the note duration past the point when the fret is released. Any attempt to do this results in a sustained note about half a semitone flat!

For this reason, the instrument sounds better when played through an echo unit as chord changes and note endings sound less disjointed. Because the pitch control is derived from the string vibration, it is essential for the guitar to be well set up and fitted with good strings, preferably nickel wound. I am presently using Superwound strings as the heavier bottom strings and nickel on steel construction give less mistracking problems than any previous type. Also the tuning holds very well. Fret buzz must be avoided at all costs unless you like yodelling guitar!

A standard problem with this particular model (GR500) is that the bottom E tends to mistrack regardless, unless played quite gently, and a couple of fret positions on the G string tend to swoop up an octave after about five seconds of sustain. Roland have not yet come up with an easy solution to this problem.

One tip on fitting strings to this or any other electric guitar is to put a piece of PTFE plumbers' tape along the nut before fitting the strings. The low coefficient of friction eliminates sticking problems encountered with even the best cut nut and it is so thin that the action and sustain are unaffected. This measure ensures that I only have to tune up once for each gig.

In spite of its limitations and the fact that playing technique needs to be careful and not too fast, the sounds available from the GR500 are most impressive. String bending and finger vibrato can also be used to simulate the performance controls of a conventional keyboard synth.

Using the polyphonic section simultaneously with the monophonic solo or external synth, gives the impression of a different lead instrument backed by a polyphonic string sound and because there are three separate outputs on the unit, the rich and ambitious can route different sections to different amps for quite stunning dimensional effects. The sound tends to be rather flat if amplified with no treatment, but a little echo and chorus will vastly improve the sound of any guitar synth. I played this guitar live at gigs for about two years and had even convinced myself that it wasn't really that awkward to get on with, when Roland brought out their GR300 range of guitar synths.

Roland GR300.


Roland GR300



During this period, no other manufacturer seemed to have made a serious attempt to produce a new guitar synth, so I tried out the GR300 at the first opportunity. Initially, I was a little disappointed in the lack of variable parameters, especially as the old GR500 had more knobs on the guitar than this had on the main synth unit. There was no proper portamento, no VCA envelope, no waveform selection and no infinite sustain. How could it possibly be as good, let alone better?

After trying the unit out, however, all doubts were dispelled — well nearly all. The synth had an oscillator for each string, each of which tracked and held tune perfectly, due to a cunning phase sync technique, and even though the sound was all processed through one filter, the effect was truly polyphonic. The best advancement was that ordinary playing technique could be used and there was even real touch sensitivity, polyphonic vibrato and polyphonic glide. I shan't go into too much detail as the review in an earlier edition of this magazine (November 1981) described the controls of this instrument in detail.

Needless to say, I arrived home with a GR300 tucked under my arm and started the real work of getting to know its strengths and weaknesses. Only minor criticisms of the instrument came to light. There were a couple of slightly dead notes on the guitar which prematurely shortened the synth note duration in these positions. This is apparently a general problem rather than just my model. The preset pitches are very useful as you can set two different harmonies to play in parallel with the guitar's pitch. However, I would have liked either a third position or a selector knob with semitone steps as it is useful to be able to call up sub octave, major fifth and one octave up without having to grovel on the floor to retune. I might be able to accomplish this by drilling holes for an extra pot and switch but I wouldn't recommend this to anyone unless they know just what they're doing.

The inside of the synth unit seems to contain a large amount of electronics and I sometimes wonder if the design could be simpler to produce the same results. Their Hall Effect volume pedal incidentally is the same, containing about half a dozen ICs and ten or so transistors. Still, it does its job very well and it's so straightforward to play that when I go back and blow the dust off the GR500, I feel as though I'm playing with gloves on. I'm now looking forward to see who brings out the next significant step and what it will be. Last year's music shows provided no clues, although I'm sure that a programmable guitar synth will not be too long in arriving on the market.

It is likely that there will soon be a digital sampling system geared up to the guitar synth, enabling the guitar synthesist to successfully emulate conventional instruments with much greater accuracy, a facility already becoming more affordable for the keyboard counterpart. One system under development for release in 1983 is the Synclavier digital guitar link to the Roland GR300 guitar synth.

I have heard rumours that someone is attempting to improve on this advanced system — something about a hollow box with wires stretched over it!


Also featuring gear in this article



Previous Article in this issue

Synclavier II

Next article in this issue

Music Maker Equipment Scene


Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.

 

Electronics & Music Maker - Jun 1983

Feature by Paul White

Previous article in this issue:

> Synclavier II

Next article in this issue:

> Music Maker Equipment Scene


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