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Moog Sonic 6

Analogue Synthesizer (Retrozone) By Gordon Reid
Published March 2002

The pioneering Sonic 6 has a complex and intriguing background, featuring not only the synth industry's most famous name, Bob Moog, but also that of an unsung hero called Gene Zumcheck — a shadowy figure now, but one whose contribution to synthesis deserves acknowledgement.

Moog Sonic 6Call me a heretic if you like, but I sometimes wonder why we make such a lot of fuss over Bob Moog and the synthesizers that bear his name. Sure, they were good and, in one or two cases, excellent, but there were an equal number of flops and — to be polite — almost as many blunders.

In part, the reverence must be due to the fact that Moog was a pioneer, a trailblazer who, back in the 1960s, offered us magical new sounds and new musical experiences. Indeed, his early instruments helped to create entire genres of modern music where none had previously existed. But is this sufficient reason to worship Moog, and to afford him the title of 'Godfather of Modern Synthesis', as many now do?

To answer this, I'm going to offer you an alternative view of the development of Moog's synthesizers. To be honest, many of the events described in this article took place when I was barely out of short trousers, and I can't be sure that they are the only interpretation of the story that unfolded between 1969 and 1972. Nonetheless, I'm fairly sure that I've got it right, so I'm going to use this month's retro to explode some myths...

The Birth Of The Sonic V

During the late '60s, RA Moog Inc. was based in Trumansburg NY, and employed an engineer and designer named Gene Zumcheck. It was Zumcheck, together with fellow engineer Bill Hemsath, who badgered Bob Moog to design an integrated synthesizer that players could use without resorting to a spaghetti junction of patch leads. Unfortunately, Zumcheck and Moog were reportedly not what you could call chums, and Moog declined to develop these ideas, so Zumcheck left the company.

Following his departure from RA Moog Inc., Zumcheck was approached by a chap named Bill Waytena, who claims independently to have had the idea that an integrated synth would be of interest to schools and colleges. Precisely how Waytena and Zumcheck (who, legend has it, were both Ukranians) met is shrouded in history. However, there's no doubt that Waytena and his company, muSonics, made it possible for Zumcheck to design and build the Sonic V — the integrated synthesizer he'd wanted to build while working for Moog.

This comprised a pair of oscillators, a diode ladder low-pass filter (which side-stepped Moog's patent on his transistor ladder filter), two LFOs, and a single contour generator — and it could be programmed and used without the aforementioned spaghetti junction of patch leads.

With its sturdy wooden case, well-designed control panel and four-octave keyboard, the Sonic V should have been a huge success. Unfortunately, it wasn't. But Waytena was no mug, and he knew why. He realised that, without a recognised name to stick on the nameplate, he was going to sell very few synths (and you thought that designer labels were a recent phenomenon?). At this point, fate stepped in.

Back in Trumansburg, not everything in the synthesizer garden was rosy. Bob Moog's engineering credentials may have been of the highest order, but perhaps his business acumen was not. Despite the explosion of interest in electronic music fuelled by innumerable, ghastly 'Moog' records in 1969, RA Moog Inc. was insolvent. By the end of 1970, the company had an empty order book, and there was significant competition in the shape of ARP, whose synthesizers offered advantages over the equivalent Moog instruments. Something had to change and, when Waytena discovered that Moog's company, and therefore the Moog name itself, was up for grabs, the pieces of the jigsaw fell into place.

Waytena was an entrepreneur, a specialist at revitalising bankrupt or insolvent companies and then selling them for a profit. So he bought RA Moog Inc. for the cost of its debts ($250,000) and moved the company to a converted gelatine factory in Buffalo, a city near the Canadian border in upstate New York. Moog hated the place, but that didn't stop Waytena from merging his two synthesizer companies there to create Moog/muSonics, an entity that soon metamorphosed into Moog Music.

At this point, let's spare a thought for Gene Zumcheck. Having (allegedly) fallen out with Bob Moog once before, he again found himself working alongside the man, and soon left the company. Once Zumcheck had departed for the second time, Moog decided to take the Sonic V and turn it into a Moog product. To do so, he made just one significant change; he returned to one of the rejected 1969 drawings for the Minimoog (one that never made it, even as a prototype), and installed the Sonic V's circuitry and keyboard into this. He then added a pitch-bend wheel and glissando control. The result was the Moog Sonic 6.

If you look at a picture of the Sonic V, you can see that Moog chose not to disguise the Sonic 6's origin. Indeed, the panels and facilities of the two instruments are all but identical. In some ways I find this quite surprising, because it's an open admission that the Sonic 6 was someone else's instrument. Indeed, it looks and feels quite unlike any other Moog synthesizer. Fully integrated, with the keyboard, controls and synthesizer circuitry built into a hinged ABS case, it is perhaps unlike any other synthesizer, period. (The EMS Synthi A and AKS are also built into an ABS case, but they both lacked a real keyboard so, for the purposes of this discussion, they don't count.)

Two Versions

In addition to changing the filter in later Sonic 6s, it appears that Moog also changed the output panel. Early models offer 'High' and 'Low' audio outputs and a single switch that selects either the internal speaker system or the outputs. My own Sonic 6 (as described in the main text) offers headphone and line level outputs, plus two switches that allow you to select any combination of internal and external amplification.

The Sonic 6

When you open the case that houses the Sonic 6 you find the keyboard, performance controls and interfaces in the lower half, with the control panel and an integrated speaker system in the upper.

Moog Sonic 6 is built into its own case.Moog Sonic 6 is built into its own case.The four-octave keyboard is particularly generous, making the instrument as large as a small polysynth, but it allows you to make the best use of the Sonic 6's duophony (of which more later). To the left of this, you'll find the limited number of performance controls. Gone are the characteristic Moog dual pitch/modulation wheels, to be replaced by a single, transversely mounted pitch wheel. Above this, you'll find the master volume control and the portamento rate control.

Behind the keyboard lie two sets of interfaces: inputs to the right and outputs to the left. The left panel offers the main output (marked 'monitor') and a headphone output, together with three switches: power on/off, monitor on/off, and speaker on/off. The panel on the right provides an external signal input (with associated gain control), a generous complement of CV inputs for the pitch, filter cut-off frequency, and output gain, plus a trigger input on a Cinch-Jones socket marked 'Accessory'. But none of this gives you an idea about the idiosyncrasies of the Sonic 6. To appreciate these, we'll have to take a closer look at the architecture itself...

Modulators, Oscillators & Other Signal Sources

Moog Sonic 6Starting on the left of the main control panel, you'll find the Sonic 6's twin low-frequency modulators. Named Waveform Gen X and Waveform Gen Y, each of these offers four waveforms (sawtooth, ramp, triangle and square) plus a Rate slider used in conjunction with either a Master frequency control or the Contour Generator. You can program the LFOs independently, and then mix and balance their outputs using the Balance X/Y knob. There are few early monosynths that offer dual programmable LFOs, and even fewer that allow you dynamically to control their rates using an envelope generator... but dual, mixable, dynamic LFOs? Right now, I can think of only one (see 'The Crumar Spirit' box later).

Moving to the right, we come to the oscillators, called Tone Generator A and Tone Generator B. Each of these offers sawtooth, triangle and pulse waveforms (the last with variable pulse width, but not pulse-width modulation), coarse tuning and fine-tuning. Underneath the panels holding these, there are secondary panels that contain the modulation options. For Oscillator A, these include modulation using the X/Y mix from the LFOs, plus the output from the contour generator. For Oscillator B, the inputs are the X/Y mix from the LFOs, plus the signal from Oscillator A (thus making the Sonic 6 a two-operator FM synth). Furthermore, Oscillator B offers keyboard scaling from zero to 100 percent, allowing you to play in micro-tuned scales such as quarter notes, or obscure avant-garde scales such as 17 and 19 notes per octave.

Moog Sonic 6But that's not all. You can select the note priority that drives Oscillator A, choosing between low note, high note, and 'off'. Since Oscillator B is always high-note priority, this means that you can play the Sonic 6 duophonically.

Moving another few inches to the right of the control panel, we now come to the Ring Modulator, the pink/white Noise Source, and the Source Mixer. The Ring Modulator offers two carrier inputs: Oscillator B and the external signal input. The modulator input can be either Oscillator A or the mixed X/Y output from the LFOs. Given that, at their fastest, the LFOs stray well into audio territory, this offers yet another flexible range of facilities, especially since you can use the oscillators' FM capabilities simultaneously with any of the four RM combinations available. The Mixer then allows you to mix the outputs from the oscillators (balanced using the Balance A/B control) with the output from the Ring Modulator, the Noise Source, and the untreated signal from the External Input.

Moog Sonic 6As you can imagine, this is a hugely flexible package of features, and it makes the Sonic 6 a natural choice for all manner of weird sound effects and spacey noises. But let me put one myth to bed right now. I've read in numerous places, both on paper and on the web that, due to outrageous tuning instabilities, the Sonic 6 is unusable as a melodic synthesizer, and that it is useful only as a generator of weird and wacky sounds. This is a load of bovine manure. My Sonic 6 is in tune within seconds and, thanks to its temperature-compensated oscillator circuits, it remains so whether left on for a few minutes or a few hours. OK, I'll admit that the octave selector is slightly out on oscillator B, and that the scaling differs between 'A' and 'B' by perhaps one percent across all four octaves. However, this is no worse than many other vintage synths I own, and an hour spent with a small screwdriver should allow me to correct even these slight errors. Indeed, my experience of the Sonic 6 suggests that it is among the most stable and reliable of the early monosynths, which may explain why Bob Moog used one as an educational aid when he toured the lecture circuit in the mid-'70s.

The Minimoog Story

After Zumcheck's departure from R A Moog Inc., Moog employees Jim Scott, Chad Hunt and Bill Hemsath continued to encourage Bob Moog to develop Zumcheck's idea of an integrated performance synthesizer. It's now long-forgotten but, without the determination of these three men, the company might have gone bust, consigning the Moog name to obscurity alongside other synthesizer pioneers of the mid- to late- '60s. Fortunately, before matters became quite that desperate, the team developed an integrated synth closely related to the modular System 10 (which itself had been co-developed by Zumcheck). Then, after building three prototypes, Scott, Hunt and Hemsath went into production (allegedly against Moog's explicit instructions not to) with the first batch of Minimoog Model Ds.

Consequently, I would like to propose two ideas that fly in the face of conventional wisdom: firstly, it would be fair to describe Zumcheck and Hemsath as parents of the Minimoog, ranking alongside Moog himself. If it had been left to Moog alone, the world's most revered monosynth might never have existed. Secondly, co-designer Jim Scott (who developed the Minimoog's contour generators) has gone on record to say that the excellence of the synth can be attributed to a series of electronic accidents and a healthy dose of serendipity-Indeed, when Moog and others later attempted to correct some of these faults, they found that the 'improvements' degraded the sound. Scott has even suggested that the classic sound of the Moog filter was an accident, a consequence of a circuit configuration needed to make it work at all.

Variations On A Theme In 'D'

All Minimoogs were Model Ds. However, ignoring minor modifications such as the colour and shape of the mod/pitch wheels, there was one area in which they changed considerably between 1970 and 1981. This was the design of the oscillators.

The first 299 units, many of which were built before Moog's move to Buffalo, used all-discrete oscillators. In other words, there were no 'chips' in them. Although these units are the hardest to keep in tune, many players believe that they sound the best. (Maybe they do, but I'll sacrifice a little je ne sais quoi for pitch stability, any day.) The next 9000 or so used a newer design based on a chip called the 3046, while the last 3000 or thereabouts were based on a temperature-compensated (and therefore much more stable) Fairchild chip called the uA726.

The sounds of the three versions were subtly different, but in the late '70s and early '80s many players upgraded older Minimoogs by replacing the earlier boards with the later ones. Nowadays, analogue anoraks throw up their hands in horror at this, but when you're on stage in front of a few thousand people it's no good explaining that your synth has luvverly discrete oscillators when all your solos are horrendously out of tune.

But who introduced the uA726 to Moog synthesizers? Zumcheck, who based the Sonic V's oscillators upon this chip. Then, when Bob Moog relaunched Zumcheck's synthesizer as the Sonic 6, he retained the design. In other words, not only has Zumcheck's role in the genesis of the Minimoog been swept under the carpet, but he was even responsible (if indirectly) for its last major upgrade!


Next in the signal path, we come to the filter. Except that we don't. Unlike every other pre-patched (ie. not modular) synth that I know, the Sonic 6 appears to present its VCA (or 'Articulator') before its VCF. If you think about it, there's no reason why this should not be a viable configuration, but it looks damn weird!

The VCA offers two signal paths: one whose gain is controlled by the Contour Generator, plus a switchable Bypass that appears to pass all the signal from the Source Mixer directly to the filter.

The Contour Generator itself is, however, the great weakness of the Sonic 6. There are only two controllable stages — Attack and Decay (which would, in normal parlance, be called Attack and Release) — plus a two-position switch that selects between an AR envelope and an ASR 'trapezoid' shape. Given the Sonic 6's huge range of modulation capabilities, and the number of envelope destinations, you have every right to expect at least two full ADSR generators, but there it is... we've identified the Sonic 6's Achilles heel.

Underneath the Contour Generator panel, you'll find the Trigger Input selectors, which offer keyboard triggering, and Gen X and Gen Y triggering (which operate regardless of the LFO waveforms selected). You can select and mix any combination of these to create strange, polyrhythmic effects — great. Unfortunately, once triggered, the Contour Generator will always complete its cycle, even when set only to Keyboard Triggering, and whether you hold a key or not. Sometimes useful for percussion synthesis, this can be a complete pain in the posterior when you use sounds that have a slow attack. You release the key, expecting the sound to enter its Release stage but it continues to swell, possibly in both volume and brightness. Not so great.

Penultimately, we come to the filter. Early Sonic 6s retained Zumcheck's diode ladder filter, but serial numbers above 1264 incorporated Moog's transistor ladder. Either way, the panel offered the usual control over cut-off frequency and resonance, with cut-off frequency modulation provided by the Contour Generator, the mixed X/Y output, and/or the keyboard (zero or 100 percent).

At maximum resonance, the filter will self-oscillate. However, on my unit (serial number 1496) the Moog filter offers progressively less resonance at lower frequencies, to the point at which self-oscillation is no longer possible. This behaviour emulates that of my Minimoog, although to a more extreme degree. The similarity should come as no surprise — after all, this is one of the Sonic 6s with the traditional Moog filter.

The final 'panel' contains the Direct Output Mixer, which allows you to mix the untreated output from Oscillator A, Oscillator B, and the Ring Modulator directly into the final output. Since these signals are not modified or articulated by the VCA or VCF, they offer quite different tones to those provided by the conventional signal path. Indeed, if youbase the main synthesized sound just on Oscillator B, and then add low-note-priority Oscillator A in the Direct path, you can not only play duophonically, but also (within limits) duotimbrally. This was amazing stuff in 1972.

Two Into One Will Go

ARP Odyssey.ARP Odyssey.I owe you an apology. This is because I claimed in an earlier Retrozone feature that the ARP Odyssey (released in 1972) was the world's first commercial duophonic synth. Unfortunately, this statement doesn't stand up to scrutiny because the Sonic 6, also built in 1972, is also duophonic.

At first look, that statement doesn't make sense — but let me explain. Remember that the Sonic 6 is, for the most part, a cosmetic rehash of the Sonic V. This means that the Sonic V, built in 1970, is almost certainly duophonic too, and if it is, it beat the ARP Odyssey to the punch by two years. (I have no way to check this. Maybe someone in SOS-land could write to tell me, one way or the other.)

So, not only was I wrong to accord the 'First To Achieve Duophony' honour to ARP, but it now appears that neither ARP nor Moog can claim to have marketed the world's first duophonic synth. Yet again, Zumcheck seems to have been ahead of his time.

In Use

In addition to its weird architecture, the Sonic 6 hides a few tricks that you probably won't discover when you first play one. My favourite involves the Gen X/Y Balance control. As already described, this balances the outputs from the two LFOs prior to applying the summed CV to the oscillators, Ring Modulator, and filter cut-off frequency. What is not apparent, however, is that if you turn this knob fully anti-clockwise and click it to the 'off' position, Gen X is directed exclusively to Oscillator A and the filter, while Gen Y is directed exclusively to Oscillator B. This is fantastic, allowing you to control the depth, waveform and rate of modulation independently for each oscillator. The richness of sound thus obtained has to be heard to be believed.

A second bonus concerns the implementation of the Glissando. When the keyboard tracking of Oscillator A is set to 'High Note', glissando affects both oscillators equally, producing the portamento effect that you hear on almost all other monosynths. However, if you set the tracking of Oscillator A to 'Low Note', glissando does not affect it. If you then play the Sonic 6 monophonically, Oscillator B glides between notes, while Oscillator A jumps directly to the new pitch. This is an uncommon effect, but very expressive.

The third bonus, for me, concerns the filter, which tracks the keyboard perfectly. When self-oscillating, it produces a gorgeous, delicate wave that is slightly more complex than a pure sine wave (and therefore more interesting) but which retains much of the sonic purity and roundness of the sine. Played with a little glissando, a little vibrato, and a moderate Attack and Release contour on the VCA, this is a superb 'lead' patch that would be perfect for much of today's New Age twiddling.

Hang on a second... if the VCA precedes the VCF, it should not be possible to articulate the self-oscillating filter. This means that that the signal flow depicted on the control panel is wrong! I can think of only one acceptable excuse for this: because the controls are mounted directly onto the synthesizer boards, it may have been necessary for electronic reasons to have the VCA components to the left of the VCF.

But to concentrate on the niggles is, perhaps, to miss the point. In 1970 (and in 1972), this was a remarkable design, and both the Sonic V and the Sonic 6 deserved greater recognition than they ever obtained.


When people tell the story of Moog synthesizers, there are many names that appear time and again. There's Bob Moog himself, of course. You're also likely to hear the names of Tom Rhea, Dave Van Koevering, and Bill Waytena (who almost certainly saved Moog from extinction). And, if you're researching the development of the Minimoog, you will probably encounter the names of Jim Scott, Bill Hemsath and Chad Hunt.

But what of Gene Zumcheck? How many of us can hold our hands up and say that we fully appreciate his contribution to synthesis? Not many, that's for sure.

This is not surprising. Bob Moog doesn't mention Zumcheck's name when interviewed for reference books such as Mark Vail's highly regarded Vintage Synthesizers. Neither does Peter Forrest in his excellent A to Z Of Analogue Synthesizers. Forrest merely says: "Whoever designed the Sonic V deserves praise: one of the earliest portable synths, it was good enough to avoid major reworking when Moog turned it into the Sonic 6." Yet it was Zumcheck who — before the development of the Minimoog — urged Moog repeatedly to design an integrated synthesizer. It was Zumcheck who designed the Sonic V (and therefore the Sonic 6), and it was Zumcheck who introduced the uA726 chip that Moog Music later adopted for its own oscillators. (See 'Variations On A Theme In 'D'' box.) Likewise, Zumcheck's contribution to duophony seems to have been forgotten.

So when we tell the story of Moog synthesizers — indeed, when we tell the story of all analogue synthesizers — perhaps we should talk a little bit less about Bob Moog, a little bit less about ladder filters and modular synthesizers, and somewhat more about Gene Zumcheck. Wherever you are now, Gene, well done — and thank you.

The Crumar Spirit

As I wrote in a previous Retrozone, the Crumar Spirit was co-designed by Jim Scott (one of the co-designers of the Minimoog), Tom Rhea (another Moog employee best known for writing many of Moog's synthesizer manuals), and Bob Moog himself. But if you stick the Spirit next to a Sonic V or Sonic 6 you'll start to notice some remarkable similarities. Take, for example, the Sonic V's (and therefore the Sonic 6's) Waveform Gen X and Waveform Gen Y low-frequency oscillators, and compare these to the Spirit's Mod X and Shaper Y. The Spirit is more advanced, and given that it appeared 13 years after the Sonic V, that's not surprising. Nonetheless, there are enough similarities between the two to raise an eyebrow or three.

Likewise, consider the dual signal paths in both synths, which allow you to mix the filtered and articulated signal with the unaffected outputs from oscillators A and B, and the Ring Modulator. And how about all three synths' ability to disconnect oscillator B from the keyboard CV, thus making it possible to use it as a drone or as a static FM carrier? These similarities are non-trivial, and are of an obscure enough nature to suggest that there is a direct line of descent from the Sonic V to the Crumar Spirit. Of course, Zumcheck got no credit for the Spirit, and this seems to be, at best, an oversight. I reckon that synthesizer aficionados have a lot to thank him for.