Yamaha GX1 Synthesizer, Part 2 (retro)

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Reviews : Keyboard

Last month, Gordon Reid told us how he found one of the world's rarest synthesizers in Australia, and of the trouble he went to to get it home. This month, he explains what it is about the Yamaha GX1 that made it all worthwhile...

 
To understand just how radical the GX1 was in 1975, you have to remember what else was available at the time. Keyboard rigs consisted exclusively of electric pianos, clavinets, organs, Mellotrons, 'string' machines and monosynths. OK, so Oberheim had already announced the 4-voice and the Polymoog was but a gnat's spit away, but only the GX1 was polyphonic and multitimbral. What's more, it had multiple keyboards, nearly every note was duophonic, and it offered patch storage.

Looking in detail at the GX1's voice and performance structure only heightens the impression that this was, and is, a remarkable instrument. Mind you, you can't do this by looking at the instrument itself, because you can only create a sound using the optional programmer and "Tone Module Setting Box", which may be even rarer than the GX1 itself.

On the GX1's top lid, above all the manuals and controls, are four panels which flip up to reveal the huge circuit boards that host the Tone Cartridges. These cartridges, which are about the size of a matchbox, each contain 26 tiny potentiometers that determine the values of the circuits creating a single GX1 Tone. In other words, each cartridge is, in essence, the top panel of a conventional analogue polysynth.

There are two types of cartridges: Fixed Tone Modules, and Programmable Tone Modules. As you might expect, you cannot adjust the Fixed Modules; these provide the 'factory' Tones supplied by Yamaha (see box). The Programmable Modules, by contrast, allow you to access the potentiometers that define the Tone. Unfortunately, you can't reach these when the cartridge is inside the GX1, so you have to remove it and connect the cable from the programmer in its place. Once attached, the programmer then duplicates that cartridge's functions, thus fooling the GX1 into thinking that the cartridge is present. Now, of course, you can adjust that Tone (but only that one) just as you would if the GX1 was a conventional synth with a control panel.

The Setting Box has two switches, a large selector with positions 1 to 26, and three lights called 'To Right', 'To Left', and 'OK'. Once you've programmed a Tone you want to store, you plug the Tone Cartridge you wish to program into one side of the Setting Box, and the programmer itself -- being careful not to knock any of its knobs or sliders -- into the other. Having done so, you set the large knob on the Setting Box to '1' and check whether the To Left or To Right lamp is lit. Then, locating micro-screw '1' on the cartridge, you turn it in the required direction until the 'OK' lamp lights. Now you rotate the selector to '2', locate screw 2, and repeat the operation. You do this until you have set all 26 screws correctly, at which point the resistances of the 26 tiny potentiometers in the cartridge echo those of the much larger ones in the programmer.
You think I'm joking, don't you? Well, I'm not. Next, you remove the cartridge from the Setting Box and insert it into the desired slot in the GX1 itself. Simple! Actually, it's not just simple, it's brilliant. Three years before the Z80 microprocessor allowed Sequential Circuits to incorporate 40 patch memories into the Prophet 5, the GX1 offered 70 Tone memories with none of the parameter quantisation of microprocessor-contolled synths.

The GX1 Voice Structure

Each voice in a Tone has just one VCO, but this is capable of producing many different waveforms simultaneously. For example, you can use the sawtooth directly, and/or pass it through a programmable band-pass filter. At the same time, you can add a sine wave and/or a pure square wave to the sound. In addition, the square wave has a second output that passes through a programmable high-pass filter. This has a dedicated volume control so that you can add it into the mix at any desired level. Similarly, a triangle wave and noise generator have individual level controls and you can add these in, too. But that's not all, because the square-wave generator offers programmable pulse width (from 50 to 90 percent) and PWM. All this, simultaneously, from just a single oscillator... it's a heady mix of features. And, perhaps because the waveshapers use discrete circuitry, it sounds great, too -- much 'fatter' than any other single-oscillator synth.

The combined mix of these seven (!) waveforms then passes through the first two VCFs it will encounter -- a low-pass and a high-pass -- before being fed to the VCA. These filters are legendary, and rightly so. Calibrated in "Harmonic Numbers" relative to the fundamental frequency, and with independently variable resonance (or 'Q') ranging from 0.5 to 15, there is nothing else that sounds like a GX1 filter. Yamaha never published a dB/octave figure for it, and some writers have suggested that Yamaha's CS- and GX-series filters only offered 6dB/octave cutoff rates. This must be wrong: you can not have a resonant 1-pole filter, and it's extremely unlikely that anybody would design a 2-pole filter with only 6dB/octave cutoff in the audio range. Most likely, all the GX1 and classic CS filters have a 12dB/octave slope, like those in Yamaha's earlier SY1 and SY2 monosynths and later CS-series instruments. The only published information, buried very deep within the service manual, is that all the filters have a frequency response of 25Hz to "10 octaves up" (over 25kHz). This is a fantastic range, and no doubt one of the characteristics that contributes to the GX1's phenomenally 'open' sound. OK, so a Q of 15 is not high enough to induce self-oscillation, but there is enough resonance to alter sounds dramatically and make them cut through any mix.

As you might expect, the filter contour generator is unconventional, and its only failing is that there is just one contour that acts equally on the LPF and the HPF. It has six parameters: an Initial Level, Attack Level, Attack Time, 1st Decay Time, 2nd Decay Time (more commonly called Release), and a Polarity switch. These make it possible to create filter envelopes that the more common ADSR cannot achieve. The second envelope generator is a conventional ADSR, and controls the VCA. However, despite their differences, both envelopes share an important feature: their fastest Attack times are a phenomenal 0.001seconds (1 millisecond). This makes the GX1 snappier than any other analogue polysynth ever built.

At this point, you may be asking where the LFOs are, together with the performance controls that you would expect on a flagship instrument. Well, you'll have to hang on a bit longer before I answer that. Firstly, we have to answer the question...

Which Tone Goes Where, Mum?

If this were any other synth, we could now say -- for example -- that each Tone has, say, eight Voices (8-note polyphony), and that two Tones make a Patch. But this is a GX1, and, for any given Tone, the relationship between Voices, Tones and Patches changes, depending upon where you insert the cartridge into the instrument. What's more, the range and nature of the controls that modify the Tone are also dependent upon the Tone cartridge's position.

Let's assume that you've programmed a handful of Tones, and you want to allocate them to the various manuals and the pedal board of the GX1. To do this, you must return to those four panels on the top of the GX1, marked Upper, Lower, Pedal, and Solo. Clearly, the board underneath a given panel holds the Tones for the named manual (or the Pedals). And that's exactly how it is... you press one of your programmed Tone Cartridges into any free slot on the desired board and, depending upon its position, you will be able to access it using the appropriate round, illuminated Tone button on the main panel.

There are forty Tone buttons -- Upper 1 to 10, Lower 1 to 10, Pedal 1 to 10, and Solo 1 to 10 -- implying that there are 40 locations for Tone Cartridges, 10 on each board. But that's not correct. Upper, Lower and Pedals access two cartridges for each Patch; the two Tones in an Upper, Lower or Pedal patch are called (I) and (II), and you mix them using the Mixing tabs on the control panel. This means that every note you play (except for Solo patches) is truly bi-timbral. What's more, you're not restricted to choosing the Tone pair selected by a single Tone button. You can press any two buttons in a rank simultaneously, and mix the (I) Tone of the left button with the (II) Tone of the right. For example, you could push down Upper buttons 5 and 7 simultaneously, and mix the Upper 5(I) Tone with the Upper 7(II) Tone. There are 55 possible Tone combinations using this scheme: 1(I) plus 1(II) to 10(II), 2(I) plus 2(II) to 10(II), 3(I) plus 3(II) to 10(II)... and so on, and each of them is freely mixable.

So that's 20 Tone Cartridges for each of the Upper, Lower and Pedals, and a further 10 for the Solo... 70 cartridges in all. Or, to put it another way, that's 55 mixable combinations for each of the Upper, Lower and Pedals, plus a further 10 for the Solo, making 175 mixable Patch combinations in all!

Perfect Pitch?

I mentioned earlier that you can modify and play any given Tone in a variety of ways, depending upon where you insert it. The most obvious of these differences is in the polyphony of the sound. The Solo manual is, of course, monophonic, as are the Pedals, whereas each of the Upper and Lower is 8-note polyphonic. This means that there are 16 independent voice boards for the Upper manual, 16 for the Lower, one for the Solo, plus three for the Pedals (I'll explain this later) -- 36 separate synthesizers in all. It's no wonder that the GX1 weighs as much as it does. That the whole thing stays in tune, especially with no auto-tuning capability, is nothing short of miraculous.

But it's not just polyphony that separates the manuals. Let's take the pitch of the sound as an example. To the left of the Tone buttons you'll find the Over Tone sliders. In normal parlance, these are pitch controls, but by now you're becoming accustomed to the GX1's oddities, so you won't be surprised when I tell you that they work quite differently from those of any other synthesizer. The GX1 selects pitches by quoting harmonic numbers relative to a 16' organ pipe. As you can see from the table, every rank of voices offers the standard pitch (1), the second harmonic (2), and the fourth harmonic (4), but other pitches are only available on certain ranks.

Upper I	1	2	4	5	6	8
Upper II	1	2	3	4	7	8
Lower I	1	2	4	5	6	8
Lower II	1	2	3	4	7	8
Pedal I	1/2	1	2	5/2	3	4
Pedal II	1/2	1	3/2	2	7/2	4
Solo	1/8	1/8	1	2	4	8

 

Now, if a setting of 1 is the same as the 16' setting on a conventional synth, then 2 is equivalent to 8', 4 is 4', and 8 (the 8th harmonic) is equivalent to 2'. More interesting than these are the 3, 5, 6 and 7 settings, which refer to the 3rd, 5th, 6th and 7th harmonics of a 16' pipe. You will never see these on the octave selector of a conventional synth, but there is one place that you will see some of them. It's on a Hammond organ and its imitators, where 3 would be the 5 1/3' drawbar, and 6 would be the 2 2/3' drawbar. But that still leaves 5 and 7. Of these, 5 would be the 5th harmonic of 16', which is 3 1/5', but there is no drawbar of this pitch. There is, however, one at half this length (1 3/5') on a Hammond, which is the 5th harmonic of an 8' fundamental. But there's no equivalent to 7 anywhere on an organ. It's unique to the GX1.
Moving on, it's not hard to recognise that 1/2 relates to a fundamental pitch of 32', and that the Pedal I and Pedal II pitches are harmonic series relating to 32' rather than 16'. This makes perfect sense, given that these are bass pedal settings. Finally, what of the 1/8 setting on the Solo keyboard? This, by analogy, is equivalent to a 128' position on a conventional synth. Sub-sub-sub bass, anyone?

As you can imagine, this huge range of pitches allows you to build incredible organ patches. From thunderous 32' bass to all manner of high harmonics, the GX1 sounds like a cathedral organ in a way that no other synth can. I've tried to emulate it on every other synth and sampler that's passed through my studio and nothing comes close. Furthermore, the enharmonic pitches allow you to create some unique 'synth' sounds, quite recognisable as GX1 patches.

Now, let's take a look at the pull-out drawer underneath the left end of the Lower manual. You'll see five banks of sliders. The first of these, marked Tuning, has four controls -- S, U, L, P -- which are additional tuning controls for the Solo, Upper, Lower and Pedals. Alongside these, a further four sliders are marked Wave Motion U, L, PI, and PII. This is Yamaha's long-forgotten fine-tuning mechanism, with the U and L sliders slightly sharpening the (II) patches of the Upper and Lower manuals respectively. The Wave Motion described is, therefore, the natural chorusing of two detuned Tones within a Patch. But what of the PI and PII sliders? These tell you that the bass pedals use three complete synthesizers per note -- one (I) and two (II)s -- and that you can detune each of the (II)s by a different amount. The depth of the resulting sound is indescribable.

Moving sideways a little further, you'll find three sets of controls, marked 1, 2 and 3, which echo the pitch selectors on the top panel. You select these 'pitch sets' using five of the buttons found between the Upper and Lower manuals. The 1, 2 and 3 buttons select the 1, 2, and 3 pitch sets from the drawer, while the 4 butto

Classifying Sounds Nothing about the GX1 is simple or straightforward. For example, rather than naming Tones, Yamaha gave each Fixed Tone Module a six-digit alphanumeric 'serial number' that classifies the type of voice it contains. The first character is a letter: A to I are "natural" sounds, J to Z are "electric". If the Tone is "natural", the remaining characters provide a shorthand for the name of the instrument and the Tone's position in the instrument. If the Tone is "electric" the characters depict the natures of the filter and amplitude envelopes, plus the oscillator waveform(s) used in the patch.

n has the preset pitching 1, 2, 4, 2, 2, 1, which is Yamaha's preferred 'organ' selection. If you want to use the 'live' sliders on the top panel, you press the black C button, which cancels the presets. Truly, the GX1 is a monster!

What About The LFOs, Guv?

Let's assume that you've programmed a Tone, decided from which manual to play it, and determined its pitch. So what's left? Well, do you remember that there are no LFOs in the basic Tone structure? This is because there is only one LFO per manual (as opposed to one LFO per Tone or per Voice), so it is included within the performance structure instead.

Let's take the Upper manual as an example. If you look to its left, you'll see the "Sub Oscillator", an LFO with six waveforms, variable speed, and three destinations: VCO, VCF and VCA. There's also a tab marked Solo: this links the LFO speed to the most recent key played on the Solo keyboard. In other words, the modulation speed of the polyphonic keyboard follows the pitch of the monophonic lead sound. Weird, and wonderful!

Sticking with Upper's modulation controls, you'll see the Random modulators. These add a small random variation to the initial value of the VCO, VCF and/or VCA at the moment you press a key. This is quite different from adding noise to any of these destinations and, used subtly, adds a pleasing organic movement to the sound as you play.
Next to the Random tabs, you'll find the Touch Response tabs: Vibrato (VCO), Wah-Wah (VCF) and Resonance. So the GX1 is pressure-sensitive too? No! The touch response in question is achieved by wiggling the key from side to side. It's the most intuitive way to add vibrato that any keyboard ever had. Once you've played this, you'll never be satisfied with conventional up/down sensitivity again.

But that's not the end of the Upper manual's modulation options. To the right of the keyboard, you'll find four switches also marked Sub Oscillator: these allow you to regulate the amount of modulation using the Knee Controller. You use your right knee to press this large metal lever to the right, and this adds yet another unique level of playability to the instrument. You'll also find Upper Sustain and Portamento controls next to the Knee Controller tabs. Oh, didn't I mention that each of the manuals has variable Sustain and that the Upper has polyphonic portamento? Oh well, there's only so much space in an issue of SOS!

Fortunately (as far as my word count is concerned) the Lower manual is a little more basic than the Upper, lacking portamento and touch-sensitivity. It does, however, retain the LFO, knee control, and Random functions.

Fine-Tuning The Sound

You might think that this would be enough for any polyphonic synthesizer, let alone the first on the planet -- but so far, I haven't even mentioned the most important sound-shaping controls. If you look to the left of the Tone buttons on the top panel, you'll see five sets of tabs. The first of these are simply marked Volume, so there are no prizes for guessing what these do. Next to these, you'll find the Brilliance and Resonance tabs for each o

Auto Rhythm George Gibbs reviewed the first production GX1 for the January 1976 issue of International Musician magazine. He described its rhythm unit as "the most realistically voiced electronic drummer I've ever heard." It just shows how much things have changed, because the GX1 has the most 'boom-chick diddely-bop' drum machine of them all. Do you remember the Roland TR77? Well, think sub-TR77, and that's what you've got. There are 12 sounds and 14 basic rhythms (see the lists on the right) and you can create up to 56 variations upon these by pressing either or both of the Variation A or Variation B buttons. But don't expect audio fireworks -- these are very basic at the best of times. Of course, since this is a GX1 beatbox, nothing can remain simple, and here's the complication: you can press multiple rhythm selectors simultaneously! The other controls are: Tempo, Swinger (which syncopates the rhythm), Volume, Balance (which mediates between bass/tom sounds and hi-hat/cymbal sounds -- the snare seems unaffected) and an Image tab which, depending upon position, accentuates the up-beats or down-beats. You start the thing using the Start switch or the "synchro", which initiates proceedings when you press a note on the Lower manual or the Pedals. Oh yes, and the Start switch is linked to the footswitch, so you can start and stop the rhythm with your feet if required. It's all horribly Blackpool Tower Ballroom and best forgotten. THE RHYTHMS March I. March II. Waltz. Swing. Slow Rock. Jazz Rock I. Jazz Rock II. Tango. Beguine. Rhumba. Mambo. Bossanova. Samba I. Samba II. THE SOUNDS Bass Drum. Bongo. Clave. Cow Bell. Cymbal I. Cymbal II. Hi-hat. High Conga. Low Conga. MA (not operative). Rimshot. Snare Drum.

f the Upper, Lower and Pedals. These control resonant band-pass filters which alter any voice dramatically. Forget your Prophet and Oberheim filters -- these are the business.
Next come the Mixing tabs already discussed, and then there's the Reverb. Two tabs determine the amount of signal directed to the internal spring reverb or, if you plug external units into the twin input/output sockets, determine the amount fed to the external boxes. Placing a modern digital reverb here sounds unbelievable -- except for one thing. The bandwidth of the GX1 is so great that some digital reverbs can't handle the signal, and alias like crazy!

If you now turn your attention to the left of the Tone buttons and Over Tone sliders you'll find the Sustain tabs for the Upper, Lower and Pedals. (Remember, you can dynamically control the amount of sustain using the Knee Controller, which gives you a remarkable degree of expression.) Next to these are the Coupler tabs. If you're familiar with church organs you'll know what these do: they allow you to play one manual from another, creating huge layered sounds at the flick of a switch. The four routings are Lower to Upper, Upper to Lower, Lower to Pedal, and Solo to Upper. The last of these is perhaps the most interesting because it superimposes the three octaves of the Solo manual on the upper three octaves of the Upper. This allows you to layer Solo (with high-note priority) and Upper while continuing to play the Upper and Lower accompaniments unmodified. It's very 'cathedral organ', but it works a treat.

The last set of tabs are called Pitch Bend, and there are three of these too: Upper, Lower, and Pedal. These add a rapid upward 'swoop' to each note at the moment you play it. This creates some classic sounds, especially if you couple Upper and Lower, and apply Pitch Bend to just one of them. The possibilities are enormous.

Flying Solo

The Solo manual is even better endowed with performance controls: it's at least as complex as most dedicated monophonic instruments, a

The Solo Keyboard I have seen the Solo keyboard described elsewhere as a 'mini' keyboard but, if you look closely at the photographs, you'll see that it is, in fact, full-width. However, each key is very shallow front-to-back, about half the depth of a conventional synthesizer key, and this is very deceptive. Despite this, Solo remains remarkably playable and, given the opportunity, you'll soon be whizzing around without a second thought.

nd also sounds more powerful than almost any other monosynth you could name. We've covered the basic voice structure of the Solo synthesizer already, but to this you can add a powerful modulation generator, additional band-pass filtering with Brilliance and Resonance controls, a dedicated 4-parameter AR pitch envelope, variable sustain, and the yummiest of ring modulators. 
This features a conventional RM oscillator and a variable-colour noise generator for some amazingly 'grungy' sounds. Next to these there's even a Sample & Hold generator which is driven by any of the 12 sounds in the Auto Rhythm generator (see box on page 264). You can direct S&H to the VCO and/or VCF, but if you choose not to select either, it acts as a complex, rhythmic trigger for the Solo sound.

But that's still not all. The GX1 Solo manual is probably the only keyboard ever built that offers three modes of touch sensitivity. First Touch is velocity sensitivity, and controls the Initial Pitch and the Attack Rate of the pitch envelope. Second Touch is pressure sensitivity, controlling pitch, brilliance, volume, and the full set of LFO parameters. Third Touch is side-to-side wiggle and, like the Upper manual, controls vibrato, wah-wah and resonance. Again, there's nothing else as playable as this, and nothing that comes closer to simulating the nuances of an acoustic instrument. And let's not forget the portamento, the speed of which you can control using... the Knee Controlle

The Who's Who Of GX1s As you might expect, very few GX1s left Japan. I mentioned those belonging to Keith Emerson and Stevie Wonder last month. Since writing Part 1 of this retrospective, I have learned that the black GX1 sold by John Paul Jones to Keith Emerson is now owned by a gentleman named Riccardo Grotto in Italy, who says that it is part of his collection of 70+ vintage synthesizers. Other users included Benny Andersson of ABBA, who described his as "without limits". Rick Wright had one, Hans Zimmer still does (thanks to Chris Cozens for reminding me that Zimmer bought Keith Emerson's white GX1 in 1995), and fellow German prog-rock icon Jurgen Fritz of Triumvirat was also a fan. In 1978, former Focus keyboard player Rick Van Der Linden even released a solo LP called GX1. Oh yes, and the Church of Scientology has one at its studios in California!

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Running the whole length of the keyboard, there's also a ribbon controller. If you press this immediately above the centre of any key it plays the pitch of that key. But, of course, a ribbon controller is not limited to exact intervals, and this means that you can play Solo much like a cello or fretless bass. Wonderful!

Wrapping Up The GX1

We're nearly finished, but a handful of miscellaneous controls are still worthy of mention. For example, next to the pitch-set selectors and Random on/off buttons, you'll find four Brilliance controls that let you brighten up the Upper, Lower, Solo and Pedal sounds at the touch of a button. There are also five "Expression Dynamic Range Compressors" (Upper, Lower, Pedal, Solo and Rhythm). To explain these, I'll direct you to the foot pedal under the instrument -- the one that looks like a simple swell pedal. In normal operation this acts as a conventional swell pedal, but it also allows you to set the amount of dynamic range it controls. In theory, this makes it possible to fade out some sounds while retaining others. I say "in theory" because I have never got this facility to work correctly, even though pressing any of the five buttons narrows the extremes just a little.

The pedal also has a small lever mounted on its upper-left corner. This controls no fewer than five functions (which themselves control many others). The

Revisions For a synth with a production run of, at maximum, 50, the GX1 is surprising in yet another regard: there was more than one revision. For example, my user manual describes 10 rhythm sounds, but my instrument has additional clave and rimshot sounds for a total of 12. Likewise, the manual does not describe the Random or Brightness selectors found between the Upper and Lower manuals of my instrument. It even includes a large colour photograph of a GX1 that lacks these. Further evidence for this comes from Dave Crombie's GX1 article in Sound International magazine in September 1978. The machine reviewed has three tabs annotated VCF, VCO and Noise Color instead of my machine's Random settings. It, too, lacks the Random and Brightness buttons between the manuals. So there were at least two revisions.

first two of these control the Upper and Lower LFOs, and you can switch these on and off just by flicking your foot slightly to the left. (Two small red lamps on the Lower control panel show you whether the LFOs are on or not.) The third is Auto Rhythm on/off, while the fourth and fifth are independent Portamento on/off controls for the Solo and Upper manuals.

Back To The Future

That just about wraps up our tour of the GX1 and, impressive though it is, it's almost impossible to convey the impact that this instrument made just 25 years ago. It's obvious that the GX1 has a number of unique facilities. But what I find more interesting is the number of features that are now being reintroduced on modern instruments. Think about the layering of independent Tones, the coupling, the range of touch-sensitivity options on the Solo keyboard, footswitches... Today we take similar facilities for granted, and a good digital workstation will offer similar features called multitimbrality, layering, and MIDI Continuous Controllers. But consider the immediacy of the GX1, and you'll find that the big Yamaha still stands alone. Whether you're interested in making the biggest electronic sounds ever heard, or prefer subtlety, it's all here.

Published in SOS March 2000