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The Guitarist's Revenge

The all-but-forgotten guitar synth is due to return to music shops with a vengeance this summer, in the shape of Roland's GR700/G707 system and a breathtaking new British design, the SynthAxe. Paul White puts both instruments through their paces.

As little ago as last August, the guitar synthesiser appeared to be something of an endangered species, with few models available and little enthusiasm for them on the part of manufacturers or designers. Now the MIDI interface has changed all that, with two such-equipped variations on the guitar synth theme — one the product of a Japanese music industry giant, the other the invention of a dedicated band of British enthusiasts — scheduled to appear on the market by the summer. Paul White, a self-confessed guitar synth addict, takes us through the background to each instrument's development, and attempts to put their enormous potential into perspective.

Roland GR700 Guitar Synth and G707 Controller

The GR700 guitar synth may be controlled from any Roland G-Series guitar controller, but the new G707 model is recommended as its unique design reduces unwanted harmonics which would otherwise play havoc with the pitch to voltage circuitry.

The 700 is the third guitar synth to be produced by Roland, its predecessors being the GR500 and the GR300, both of which had their own strengths and weaknesses. As I own both previous models, I was particularly interested in seeing how this new model compared in terms of facilities and playability.

Before starting the review, it's worth going over the operational principles used by the Roland guitar synths and the reasoning behind them. In order that normal playing techniques may be used (including string bending and vibrato), Roland's engineers decided that the synthesiser circuitry should follow the pitch produced by the guitar strings, and this approach instantly raises some serious design problems.

First, a vibrating guitar string produces not only its fundamental frequency but also a complex series of harmonics which shift in amplitude as the note decays. These harmonics have to be stripped away from the signal before conversion, otherwise the pitch to voltage converter becomes hopelessly confused. Secondly, a guitar has six strings, and in order to separate the notes produced, an individual pickup is needed for each string. Roland have solved this particular problem by means of their hexaphonic pickup, which has six individual magnetic circuits within a single pickup housing. This is mounted very close to the strings, near to the bridge, in order to eliminate crosstalk from adjacent strings. Lastly, a guitar's signal gets weaker as each note dies away, and some system has to be devised such that the note shuts off gracefully rather than gargling into obscurity as the pitch to voltage converter loses track.

Roland's previous guitar synths solved this last problem in two different ways: the GR500 had an electromagnetically induced, infinite sustain system so that the situation never arose, while the GR300 coupled the string amplitude to a voltage controlled amplifier, so that as the guitar note decayed away, the amplitude of the synth note decayed with it.

The GR700 utilises two different approaches so that different types of sound are treated in different ways.

A system known as quantisation is available, and this rounds off the note being played to the nearest semitone. The beauty of this system is that, for the first time in Roland guitar synth history, a note can be made to sustain after releasing the string. If this was attempted on the old GR500, the pitch would become indeterminate at the instant of release, and an unacceptable amount of pitch droop was therefore evident during the release period. With quantisation, this droop is rounded up to the nearest semitone so that the pitch during the release period remains precisely in tune. Of course, this system restructures any attempt at string bending into semitone steps, and as a result should only be used on voicings that have some sort of release period, or those for which pitch bending effects would be inappropriate.

The alternative system, suitable for voices with no release time or for those where string-bending exists as a viable musical proposition, revolves around letting the synthesiser amplitude die down as the string amplitude decays, and allowing it to cut off instantly when the string is released.

The G707 Guitar

The controller is more than a little unorthodox in its aesthetic design, bearing as it does a closer resemblance to a Dalek's handbag than to an electric guitar. Instantly noticeable is the black bar joining the headstock to the body: this innovation is intended to cut down unwanted neck vibrations which would otherwise produce mischievous harmonics, thus causing dead spots at certain points on the neck.

Apart from this damping bar and the rather extrovert shape, the guitar looks and feels reassuringly ordinary, and indeed, it's one of those guitars that feels instantly familiar as soon as you pick it up.

The two pickups are fairly standard humbuckers and these are selected by means of the usual three-way switch, a single volume and tone control being provided for modification of the conventional guitar sound. The hexaphonic pickup is discreetly positioned next to the bridge and the guitar connects to the floor unit via a 27-way multicore cable terminated in locking multipin plugs. The guitar is also fitted with an efficient vibrato arm which produces the minimum of tuning problems, due to the roller bridge design.


Apart from the conventional guitar controls, the volume control of which acts as a master for both guitar and synth, there is also a balance control which permits the mix of guitar and synth sounds to be varied. The three-position mode switch cuts out the synth sound in position one, while in the other two positions, both guitar sound and synth sound are available but with differing picking thresholds, position two being the most sensitive.

In much the same way as the GR300 system, vibrato may be introduced by means of two touch plates near the treble pickup, one to activate the vibrato and the other to either switch it off or to enable momentary vibrato to be applied. Vibrato parameters such as speed and delay are decided by the programming of the sound currently being used. The vibrato depth knob gives further control and may be turned down to prevent accidental switching of vibrato when not desired.

Two further knobs are provided, these being labelled cutoff frequency and edit. These controls are only operative in edit mode, the cutoff frequency controlling the filter and the edit knob being assigned to other parameters as required. If an earlier G-Series guitar controller is used, the resonance knob is used as the edit control.

The Floor Unit

The voice circuitry of the GR700 is essentially that of the Roland JX3P, a versatile six-voice polysynth featuring two DCOs per voice and enough memory to store 64 user-programmable sounds. Like the JX3P, the GR700's sounds may be set up by editing one parameter at a time or, by using the optional PG200 programmer, you can twiddle all the knobs at once, just like a conventional analogue synth.

On encountering the GR700 for the first time, the things you notice initially are the large footswitches and the huge numeric LED display. There are eight numbered footswitches which, in conjunction with the 'bank' switch, can be used to access all 64 stored patches, configured as eight banks of eight sounds.

A hold pedal is provided which causes any sound in progress to be held indefinitely at its programmed sustain level, and this facility may be programmed to operate on any or all strings for a given patch. The edit switch may be used during programming or, alternatively, to enable the cutoff frequency control on the guitar to bp used during performance.

In addition to the 64 patches stored in memory, a non-volatile RAM pack is available, and this permits virtually instant storing and loading of a further 64 sounds, enabling a permanent library of patches to be built up. The numerical indicators show the patch number currently in use and, in edit mode, they indicate the parameter number and its data value.

There is also a further bank of small pushswitches which would normally be used during programming or editing patches, and include settings relating to memory, string selection and dynamics.

Both synth and guitar voices have separate outputs and the synth output is in stereo so that the built-in stereo chorus can be used to full effect. These outputs are available on both standard jacks and balanced XLR sockets, and an extra jack is provided so that a volume pedal can be connected to control the filter cutoff frequency.

The GR700 can be used to control other MIDI synths via its own MIDI connection: this transmits note on/note off and dynamics information, hold on/off and patch selection. MIDI channel number is fixed at one. Because keyboard information is chromatic by nature, normal string bending effects are not possible using the external synth. If this is attempted, semitone steps will result. In order to get the GR700 to send more than note and dynamic information, various function keys must be held down as the unit is powered up, and this procedure is described in detail in the owner's manual.

Playing Test

It transpired that the new unit which we unpacked and subsequently played had not been set up correctly: our musical efforts were transformed into something resembling the Grimethorpe Colliery Brass Band being tickled during rehearsals.

The hexaphonic pickup was mounted too far away from the strings and, when this was corrected (as shown in the Roland handbook), things began to improve. Once this adjustment has been made, it is then necessary to set the sensitivity for each string using six preset pots, accessible by means of a panel on the rear of the guitar.

Once thus set up, the guitar responds reasonably well to normal playing, though sloppy fingering or fret buzz is rewarded by Grimethorpe Revisited. However, it's quite reasonable to expect to make some concessions when playing this instrument and, having tamed the infamous GR500, I think I could live with the GR700 after only a short rehabilitation period.

I think it goes without saying that these sorts of sounds have never been available to the guitarist until now, and even by keyboard standards, the JX3P voicings used are very impressive.


This instrument makes it possible for the guitarist to produce sounds hitherto inconceivable but, in return, he must play cleanly, thoughtfully, and above all, ensure that the pickup spacing and string sensitivities are always optimised. It's no use setting the synth to a violin sound and then playing Van Halen riffs, and still expecting to sound like Paganini! If on the other hand, you set up a brass sound and play the part of a brass section, then you'll be rewarded by a pretty convincing musical impression.

Finally then, it would seem that in spite of the initial difficulties, the GR700 represents significant progress in the field of affordable guitar synthesis, and I'd say that any guitarist wanting to expand his horizons should give it a try. Remember though that it takes some getting used to, so sit down in the shop with one for at least an hour or two (assuming they'll let you...) before making up your mind.

Roland have informed us that all GR700 guitars will be checked at the factory before being despatched to dealers, and that a new tuning routine has also been included.

The SynthAxe

Although its appearance is pure science fiction, the SynthAxe has been under development since 1978 and is the product of thousands of hours of research. During that year, BBC music producer Bill Aitken and engineer Mike Dixon stopped merely talking about the possibilities of controlling a synthesiser from a guitar-like instrument and set about turning their ideas into reality. A first-rate digital designer was needed and Tony Sedivy accepted the challenge, largely because the task was considered to be impossible(!)

One of the first requirements was a polysynth to control and Bill found a Yamaha CS80 at a giveaway price, the latter being due largely to its unscheduled descent down an elevator shaft. Unfortunately, the ground broke more than just its fall and Mike and Tony had the rather thankless task of rebuilding it.

Before deciding on the way in which the instrument should operate, the playing technique of a wide range of guitarists was studied, and various parts of the instrument were then built in the form of test jigs to test system and transducer designs.

At this stage, a Data General Nova mini-computer was used to control the system but this was later to be replaced by onboard microprocessors. However, finance was beginning to become a problem, and this was only resolved when Virgin Records agreed to invest in the project.

As the SynthAxe team worked on, the Fairlight CMI gradually became better and more widely known, and turned out to play quite a big part in the SynthAxe's development. During a trip to Australia, Bill Aitken met Fairlight's Kim Ryrie and the SynthAxe project generated such interest that Fairlight actively encouraged development by supplying special circuit cards and a PROM blower, along with the CMI purchased by SynthAxe. The outcome of this is that the CMI system doubles as both a musical instrument and a 6809 development system.

By October 1983, the various test jigs had been bolted together into a playable form and this has since been used as the development prototype.


Because of its ungainly appearance (and the bolt through the neck), this was nicknamed Frankenstein, resembling as it did a pile of computer cards bolted to the end of a very odd guitar neck. Although difficult to play, it gave the designers a good measure of moral support by virtue of the fact that it was playable at all.

Several top guitarists secretly tried Frankenstein and their comments were analysed before the final production design was finalised. Although the first production model is not yet complete, E&MM staff have seen the improved features in the form of test jigs, diagrams and sub-assemblies, and we are optimistic that the production SynthAxe will live up to or exceed most expectations.


The layout of such a radical instrument is all-important, and mercifully the long two-octave neck provided few headaches: as the higher frets are more widely spaced than those on a conventional guitar, the scale length is rather great and so the angled neck was developed with ergonomics - as opposed to appearance - in mind. As the strings produce no note as such they are not tuned, and a completely separate set of strings is used for the left and right hands in order that the maximum amount of pitch and dynamic information may be interpreted by the electronics.

The body is a rigid foam moulding which combines physical strength with light weight, and the complete SynthAxe is expected to weigh no more than a standard Fender Telecaster. Getting all the complex electronics into the body was no easy task and Ken Steel, the mechanical designer, had to resort to five-layer computer-designed PCBs to make everything fit.

The Neck

Unlike conventional necks, this one is of a constant cross-sectional profile and is fabricated from an aluminium extrusion. The frets look normal, but close examination reveals that they are made from several segments so that the strings can make electrical contact only with that part of the fret. Electrical contact between the strings and the frets produces a unique digital code which is interpreted by one of the onboard 6809 microprocessors dedicated to scanning the fingerboard logic. String-bending is detected by moving-coil angle transducers at the end of each string and then fed information to the microprocessor, which calculates the required pitch change for each fret position, while the degree of pitch-bend itself is variable, enabling dramatic effects to be produced without slicing your finger ends.

In order to simulate left-hand damping, each string is connected to a touch sensor which utilises two different electronic principles simultaneously to ensure foolproof operation.

The Body

Mounted on the body are the trigger strings, an electronic vibrato arm and the trigger keys. The trigger strings are sensitive to picking dynamics, thanks to a novel hall-effect transducer system and, like the neck strings, they are also responsive to damping. The trigger strings are normally used to trigger sounds that have a rapid attack and a natural decay, pianos, glockenspiels and other percussive sounds being included in this category. Sounds having a slow attack and long sustain are triggered from the six trigger keys which are velocity sensitive and have an aftertouch pressure system. Although these keys are a radical departure from guitar or guitar synth design, they are both useful and surprisingly easy to live with.

The Group and Master Trigger Keys are conveniently located near to the six trigger keys and enable either the bottom three or top three strings, or all six strings together, to be played simultaneously and sustained indefinitely. There are also two Auto Trigger Keys, one by the trigger strings and one by the trigger keys, and depressing either one of these permits playing to be carried out entirely by the left hand. Thanks to these some very fast runs are possible, and by using these switches in their locking rather than momentary modes the neck may be played two-handed, rather like the Chapman Stick.

Pedal Unit

The SynthAxe connects to its pedal unit via a 14-way cable and three major functions are made available: Automatic Hold, Automatic Capo, and left-hand String Damp Disable. Depressing the Hold pedal sustains any note combination currently being played. This allows entirely new and quite fascinating drone effects to be combined with melodic playing, and it's easy to envisage new performance styles emerging from this feature.

The Automatic Capo Pedal permits the positioning of a purely electronic capo at any position on the neck and furthermore, the capo isn't limited to a barre - it can also be chord shaped. To exploit this feature further, it's possible to play both above and below the capo, opening up yet further avenues for new playing techniques, while by using the Left Hand String Damp Disable, it's possible to play a chord and then, whilst it continues to sustain, play a completely different chord or series of notes on top of it.

The SynthAxe works via a MIDI interface, and while this opens up a number of interesting possibilities, limitations could be imposed by an inappropriate choice of synthesiser. For example, choosing a synth with no keyboard dynamics would preclude the use of the dynamic facilities of the SynthAxe. Because of these limitations, SynthAxe are compiling a list of suitable MIDI synths for use with the system and this will be updated as new models become available.


An optional control console is being made available which can link up to eight synths to the SynthAxe and provide instant switching from one to the other. The console will also permit various transposition effects to be implemented and stored in semitone steps. Up to eight transpositions or capo settings may be stored in this way and it's also possible to change tuning with the synthesiser being controlled simultaneously.

And as if all these facilities weren't already mind-boggling enough, there is a proposed expander pedalboard under development, to control further effects such as pitch glide.


Although the first SynthAxe production model is not expected to be available until June of this year, what we saw was enough to convince us of the enormous potential of this remarkable instrument. To be able to fingerpick a grand piano or apply a bit of vibrato arm to a string quartet is certainly a novel experience, and as already mentioned, the unique facilities offered by this system could well foster a variety of new and exciting playing styles.

Before you reach for your Access card, it's only fair to warn you that the price will be in the order of £10,000, though a less sophisticated version is scheduled to appear in a year or so which may retail for as little as £3000, this price to incude a suitable synthesiser for sound-generation.

There are bound to be one or two Luddites who will point out that you can buy an awful lot of piano lessons for £10,000, but the SynthAxe is capable of producing music that would be impossible on either a guitar or a keyboard, lifting it well above such considerations.

The first models will be available this summer and will be distributed in the UK by Syco Systems.

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Boss DD2 Digital Delay Pedal

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


Electronics & Music Maker - Jun 1984

Review by Paul White

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