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Guitar Synthesizers

A Personal Journey By Paul White

Paul White playing his Roland GR-500 guitar synth driving the Powertran Transcendent 2000 synth (far right).Paul White playing his Roland GR-500 guitar synth driving the Powertran Transcendent 2000 synth (far right).

SOS's Paul White has been fascinated by guitar synthesizers ever since he first encountered one and has owned or tested most models over the decades. Here's his story...

Having graduated from drums to guitar during the 1970s when I was an electronics apprentice with the Ministry of Aviation at RSRE Malvern, I developed a fascination with synthesizers — I loved the noises they made but I found the keyboard too alien a concept to come to grips with. There had already been some early guitar/keyboard‑like products such as the Vox Organ Guitar, which used split frets wired so as to form switches when the strings were pressed onto them, but performance was strictly one‑handed and fret oxidisation made it very unreliable. I tried one in a local music store and was not impressed. However, I continued to followed the progress of guitar synthesis and in the 1970s very nearly bought an EMS Synthi Hi‑Fli until I realised it was really just a hyped up FX box and not really a synth at all in the accepted sense of the word.

In 1977, ARP launched the Avatar, essentially an enhanced ARP Odyssey that took its input from a hex pickup that you had to fix to your own guitar. I went out and bought one, tried it, found it didn't work nearly as well as the brochure promised and promptly took it back to the store to be exchanged for the equally new Roland GR‑500. I'd seen Adrian Lee demonstrate one for Roland at the British Music Fair and he made it sound amazing. The GR‑500 came with its own special Les Paul shape guitar, built for them by Ibanez, complete with hex pickup and a chunky multicore cable. That guitar weighed a ton! I was playing in a prog rock trio at the time so this allowed us to make all kinds of big and impressive noises without adding a keyboard player. The GR‑500 wasn't without its faults, but my affair with guitar synths had begun. 

Roland GR‑500

The first version of the GR‑500 used the signals from the strings themselves, via the hex pickup, to create the sounds — a kind of poly fuzz for the pseudo string pads and a mono lead voice complete with resonant filter and envelope shaper. You could also have bass on the lower strings, achieved via separate octave dividers on each string. Shortly after its launch, Roland changed the circuit to a VCO for the mono synth section, which meant you could have vibrato and portamento — and they were kind enough to update mine free of charge. The main problem, other than a huge tracking delay for the VCO, was that they hadn't done much in the way of temperature stabilisation, so after taking the synth from a cold van into a warm gig, the oscillator pitch was invariably still drifting by the time we finished the last song of the night. I managed to improve this somewhat by making a little insulating jacket from expanded polystyrene to go around the VCO. Now without effects, the thing still sounded like a budget mono synth accompanied by a polyphonic kazoo, but add some chorus and a bit of echo and it was transformed into a real prog monster. It was on this instrument that I wrote tunes with titles like 'Busfare For The Common Man'.

Paul White with Roland GR-500 and Transcendent 2000.The author with Roland GR-500 and Transcendent 2000 c.mid-1970s.Roland had also equipped the GR‑500 with a CV and Gate output — these were pre‑MIDI days — so I built myself a Powertran Transcendent 2000 mono synth from a kit and mounted this behind the GR‑500 synth unit. A simple mod allowed its vibrato depth to be controlled from a Coloursound volume pedal to which I added a spring so that it would always return to the 'no vibrato' position when released. The combined output of this monster, which I nicknamed Orac after the computer in Blake's Seven sci‑fi BBC TV series, was fed through a DIY keyboard combo, complete with EHX Clone Theory Chorus and a Carlsbro BBD echo box, while the guitar sound went through a regular amplifier. I didn't much like the sound of the GR‑500 guitar pickup so swapped it out for a DiMarzio humbucker and took its output from a separate socket. 

You had to play the GR‑500 really cleanly to prevent glitchy pitch swoops and it helped to use slow attack sounds to hide the tracking latency, but the instrument had its good points, not least infinite sustain on any fretted note. This was achieved by feeding signals from six amplifiers into the six guitar strings from the bridge end where insulators isolated the strings from each other. All the frets were wired to ground [earth] so the neck end of the string was grounded when fretting, causing current to flow. A magnet, in the place where you'd expect to find a neck pickup, interacted with the current passing through the string and kept it vibrating in accordance with Faraday's Law — loud enough to keep the synth's pitch tracker happy but at a level low enough not to affect normal guitar playing too badly.

I used this unwieldy rig until the GR‑300 was announced in 1979. Of course, I bought one! This still required you to use Roland's own guitar with a built‑in hex pickup, but the guitar itself was a rather nice Ibanez‑built instrument (there was a choice of models), somewhat lighter than the one Ibanez built for the GR‑500, so I wasn't too unhappy. Some people cite the GR‑300 as the first playable guitar synth but I produced a number of recordings using the GR‑500, so it can't have been totally unplayable. Having said that, I later bought it back from the guy I sold it to, tried playing it again, then promptly sold it to someone else.

Roland GR-300 polyphonic guitar synthesiser floor unit.Roland GR-300 polyphonic guitar synthesiser floor unit.My shiny new, bright blue GR‑300 was configured as a floor unit and incorporated some ingenious circuitry that used the signal directly from the strings to reset a ramp generator so as to produce a sawtooth waveform. Phase‑locked loop oscillator circuitry was utilised to produce pitch‑shifting, vibrato and pitch glide. There was basic envelope filtering and a further nice touch was the capacitive sensor plate under the bridge pickup that let you bring in vibrato just by touching it. Another sensor plate on top of the pickup activated the pitch glide, but as I kept touching that one by mistake, I taped over it. As with the GR‑500, there were no effects so the thing sounded horribly dry until I put it through chorus and delay. I have to say that it didn't sound as big and dramatic as the GR‑500 and there was no mono voice that you could noodle on while previously‑played chordal notes sounded. There was no infinite sustain either and the sound range was also quite limited covering, in the main, pseudo‑string and pseudo‑brass sounds — but it was very forgiving to play and had no latency issues. I played a lot of gigs with that little blue box and made a lot of use of that touch vibrato feature.

In the mid to late '80s, it suddenly seemed as though guitar synths were going to be the next big thing and SOS were invited to see things like the exotic and costly Synthaxe, with its angled neck. This instrument used separate fretting and plucking strings so it couldn't be used as a regular guitar. It also had a set of keys on the body. We saw the Yamaha G‑10 strung with equal thickness strings, the Casio MIDI Guitar and various other diversions but of these, only Casio's MIDI Guitar was based on a real, playable guitar and many of these instruments are still in use today. The others may have been designed to play in a guitarist‑friendly way but they were not, by any stretch of the imagination, guitars. If you are happy with a guitar‑shaped MIDI controller that isn't actually a guitar, Starr Labs Ztar or the You Rock Guitar is as good as anything.

Roland, to their credit, continued to pursue the idea of adding synth capability to real guitars. I recall reviewing the Roland GR‑700 in 1985, their first guitar synth with MIDI, which came with a futuristic silver guitar fitted with a damping bar that extended from the body to the headstock. Its sound engine was based on the JX‑3P synth. At the time I described it as looking like a 'Dalek's handbag', a term that has apparently stuck.

The original GK-1 hex pickup controller.The original GK-1 hex pickup controller.In 1986 Roland eventually moved from custom guitars to the GK pickup paradigm where you could either buy a 'Roland Ready' guitar with a hex pickup already built‑in or add a GK pickup to your own guitar. Other manufacturers, such as Godin, Washburn, Fender and Ibanez also built guitars with integral hex pickup systems conforming to the now standard Roland 13‑pin DIN connection format. Yamaha also offered a stand‑alone guitar‑to‑MIDI converter rack unit, the G50.  A big benefit of MIDI is that external sound modules can be controlled from a MIDI guitar synth to offer a wider range of sounds. In 1992 Roland, launched the GK‑compatible GR‑1, which used sample‑based sounds and I seem to recall owning one for a while. There was still a slight tracking delay and a propensity to play random pitches in response to sloppy playing but, on the whole, it worked well for something developed so long ago.

Roland GR‑09

It wasn't until the launch of the affordable Roland GR‑09 floor unit in 1994 that I bought another guitar synth. The GR‑09 tracked fairly well, albeit not quite as quickly as more recent models, but it came loaded with some usable sample‑based sounds, albeit fairly safe Sound Canvas‑style GM patches. When the larger GR‑33 came out some six years later with more features and better sounds, I upgraded to that and I still have it in my 'cupboard of eternal darkness'. However, I have not used MIDI guitar systems outside the studio in recent years, because I find they are just too much hassle to set up as you need separate amplifiers to do them justice and additional pedals to control them and adjust their volume. And in spite of the faster tracking, it is still very necessary to play cleanly to avoid randomly‑pitched squeals. Newer models such as the Roland GR‑55 emerged and I took a look at them too but wasn't tempted to buy anything new until more recently.

The V-Guitar Synthesizer module, the VG-99.The V-Guitar Synthesizer module, the VG-99.

I did use a Roland VG‑99 live for a while though and I still have it in my studio. While not a synth, it does share some synth‑like attributes. It evolved from the earlier VG‑8 and VG‑88 and still requires a GK hex pickup. It combines guitar and FX modelling with some synth‑like sounds (HRM or Harmonic Restructure Modelling synthesis) generated by reshaping the harmonic structure of the guitar notes being played into it. In combination with the onboard effects, that makes it capable of producing some very organic sounds that fall someway between guitar and synth. 

A paradigm shift came about just a few years ago when it became possible to extract polyphonic information from a standard guitar output.

Polyphony

Various guitar synth pedals and compact guitar‑to‑MIDI boxes have been available for a long time but until recently they only worked correctly if fed with a monophonic source — chords would just confuse them. A paradigm shift came about just a few years ago when it became possible to extract polyphonic information from a standard guitar output. TC's Polytune used the principle to show the pitches of all six guitar strings at the same time while Electro‑Harmonix followed their HOG and POG pedals with the B9 organ pedal — a polyphonic processor pedal that works from a standard guitar, to produce a very convincing tone wheel organ sound. This was followed by other 9‑series pedals offering Mellotron, Keyboard and Synth sounds. The inner workings are somewhat secret but some form of polyphonic pitch extraction seems to be going on, if only to control the filters applied to each note.  

Electro-Harmonix B9 Organ MachineElectro-Harmonix B9 Organ Machine.Currently I gig with an Electro‑Harmonix B9 organ pedal that can be brought in behind the guitar sound, but getting the best out of that proved to be no simple matter. Organs are not velocity‑sensitive so I needed to put an assertive compressor pedal before the B9 to even things up. It is also vital to have a controllable Leslie‑type effect after the pedal to make it sound completely realistic, so I opted for a Neo Mini Vent, which sounds very authentic with a lovely speed‑up, slow‑down dynamic. It turns out that during a typical song you end up changing speeds every few seconds as part of the performance, so I had to buy a stool so that I could sit down for the songs where I used it. Then I had to add a volume pedal to bring the organ in and out while playing. I feed the Leslie output to the PA rather than to my guitar amp in order to obtain full bandwidth, stereo sound, which means more cables. By the time I'd done, half my pedalboard was taken up with kit associated with the B9 — but it was worth it.
 
On the software front, Jam Origin's MIDI Guitar software proves that real‑time, low latency, polyphonic pitch‑to‑MIDI can be made to work from a conventional guitar. MIDI Guitar, available for both MacOS and Windows, must be one of the best kept secrets in the music world but it works astonishingly well with its operation being underpinned by machine learning. As Digital Signal Processing grows more powerful, this type of technology is only going to get faster and more accurate, but even now it is very usable and in the studio I tend to utilise Jam Origin's MIDI Guitar most of the time when recording software instrument parts. It gets the job done without me having to set up any special kit or change guitars. All you have to remember is to feed it clean guitar, not a signal smothered in effects. Any spurious notes generated by sloppy playing are easy to clear up, since rogue notes are usually short in length and of low velocity and thus easy to spot in your DAW's piano‑roll editor.

Boss SY

Roland's guitar arm, Boss, combined guitar effects with their take on poly pitch processing to produce the Boss SY‑300, a small blue pedal unit that creates analogue‑like synth sounds from a standard guitar input. This was an attempt to hark back to the simpler days of the GR‑300, but with more tonal variety and without the need for a special guitar or GK pickup. On the whole it works well giving guitarists access to synth‑style pad, lead and bass sounds. I have one in my studio where it gets pressed into service on some of my more ambient music projects — where combining it with plug‑in effects, playing with an eBow or using it to process slide guitar all creates interesting results. However, its built‑in effects section is seriously impressive too and many of its best sounds combine synthesis and processed guitar. Best of all is that it comes with a free software editor that makes it easy to create your own sounds or download sounds other users have created and shared.

Boss's SY-1000 guitar synth.Boss's SY-1000 guitar synth.

Then at NAMM in January 2020, the Boss SY‑1000 was unveiled. I don't own one yet but I wrote the SOS review, so it's only a matter of time before I give in to temptation! Hex pickups still provide the fastest and most accurate pitch‑tracking as they give excellent string separation and the SY‑1000 needs a hex pickup to get the best out of it, though many of its sound generators will also work with a standard guitar. It might best be described as an 'SY‑300 on steroids' with the addition of a new Oscillator voice combined with an extended set of Boss flagship effects.

There's a full review in Sound On Sound April 2020 issue but it is worth covering some of its more salient points. Each patch can combine up to three synth voices and one processed guitar voice with comprehensive routing and FX so there's a lot of scope for big, atmospheric sounds, albeit still analogue in nature. Used with a GK pickup, the Oscillator synth voice can become a multi‑waveform polysynth with vibrato, portamento and all the expected envelope, filtering and sequencer tricks, but for me it works well set to a single voice so that as you pick your way through chords, the lead voice follows while a chordal pad sound plays on one of the other poly sections — just like my GR‑500 did all those decades ago. Its ability to track the input appears to be very fast and I also found its MIDI output to be faster and more reliable than on earlier Roland/Boss guitar synths, making it a good choice for controlling virtual instruments or external sound modules.

So far this has been a condensed version of my own experience of guitar synths in the studio and when playing live. It is by no means exhaustive and it would be remiss not to mention Fishman, who have also worked hard to make the hex pickup approach work as well as possible (see TriplePlay SOS review). One thing I can say, for sure, is that my guitar synth‑buying days are probably not over yet.

GK Pickup

Roland's add‑on hex pickup is now in its third revision, the GK‑3, though all GK pickups work on the same general principle. The pickup itself is very narrow and incorporates hum‑bucking technology to minimise interference that might otherwise confuse the pitch‑tracking system in the connected GK‑compatible device. It connects to a small control unit that can be attached to the guitar body in any convenient position, though for non‑invasive fixing there's the choice of double‑sided adhesive tape or a small bracket secured by the strap button. The pickup itself may also be fixed using the included double‑sided adhesive pads and spacers or it can be fixed more permanently using two small woodscrews. Guitars with Les Paul‑style bridges can also make use of an adaptor plate that is held in place by the existing bridge pillars.

Roland GK-3 hex pickup.Roland GK-3 hex pickup.

The signal from the pickup goes to the control unit which is fitted with a 13‑pin DIN connector for onward connection to the receiving device. There's also a link jack that allows the normal guitar output to be sent via the controller, down the 13‑pin cable and on to the receiving device, most of which have a Thru connector that allows the regular guitar signal to be sent straight to a separate amplifier. One advantage of connecting this way, other than minimising the number of cables, is that the controller includes a switch for selecting Guitar, Mix (GK and Guitar) or GK‑only. A rotary control acts as a remote volume control for the connected GK‑compatible device and there are two buttons that may be used for patch up/down selection, although they may have other functions depending on which GK‑compatible device is connected.

Most six string guitars (bass versions are also available) can be fitted with a GK pickup and that includes acoustics, though instruments with Telecaster‑style 'ashtray' bridge plates are the exception as it is essential that the pickup is mounted very close to the bridge. It is also crucial to adjust the pickup distance to the strings (using the included shims) as per the instruction manual, and in the case of the GK‑3, there's also a physical adjustment that can change the curvature of the pickup slightly to match the fingerboard radius.