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Moog Mavis

Semi-modular Synthesizer By David Glasper
Published July 2022

Moog Mavis

Meet Mavis, Moog’s affordable semi‑modular with more than a few tricks up its sleeve.

Back in 2014 Moog released a small and rather unusual synth called the Werkstatt ø1. Originally conceived as a project for Moogfest 2014’s engineering workshop and never intended for general production, the plucky Werkstatt proved so popular with its makers that it soon found itself on sale to the general public.

Aside from its unconventional development the Werkstatt was unusual in three ways: one, it came as a kit and required assembly; two, it sported a pin‑connector patchbay (with optional 3.5mm breakout board); and three, it was much, much cheaper than Moog synthesizers normally are. Presumably development on the semi‑modular Mother‑32 was well underway by the time the Werkstatt came along, but to everyone outside the company it was the first indication that Moog were considering a new direction. Eight years later it seems a safe assumption that the majority of synths sold by Moog are black, semi‑modular and much cheaper than Moog synths used to be. Moog have moved on, and the plucky Werkstatt which may or may not have inspired this new direction, has moved on too. It returns now, reimagined as the Mavis...

Much like Gandalf The White, the Mavis bears many similarities to its first incarnation, but is generally better, more powerful and enjoys an assured maturity perhaps lacking in the original. This is not the result of a touch‑and‑go battle with the forces of darkness, but more likely because of a more conventional route into production than the Werkstatt and Moog’s subsequent experience in building very tightly engineered semi‑modular synths. Like its predecessor, the Mavis is also a single‑VCO, semi‑modular analogue synth that requires assembly, but it has gained extra patch points, a Utilities section, a wave folder(!), a four‑stage envelope and all sorts of other useful functions. In fact at this stage we’ll stop comparing the Mavis to the Werkstatt (and Gandalf) and concentrate on it as a synth in its own right.

Some Assembly Required

Building your Mavis couldn’t be simpler. There’s no soldering involved and the only tool you’ll need is a small crosshead screwdriver. If you don’t own a crosshead screwdriver you should buy one anyway. They’re brilliant. The whole process is very clearly described in the included quick‑start manual (more on that in a moment), but it basically amounts to screwing the PCB to the front panel, the font panel into the chassis and then screwing on the 24 patch‑point hex nuts with the tool supplied in the box. If you’re planning to Eurorack Mavis (see box), the chassis makes a handy platform to protect the PCB while you screw on the patch nuts.

It’s simple to assemble the Mavis, but it’s also satisfying and fun, and there’s even that familiar tingle of ‘will it catch fire’ you get when you power up any homemade electronic device for the first time. And for the record, no, it didn’t.

To return to the subject of the manual; the Mavis manual is excellent. Just as good as the Moog Sound Studio ones I’ll be banging on about momentarily in the nearby box, and written in a way that makes the Mavis as accessible to the complete beginner as to anyone else. Sadly, though, it’s not included in the box — it’s only available as a PDF from Moog’s website. It is very good, though.

The Synth

So having built your own synthesizer, sort of, what kind of synthesizer is it? Well, on the face of it, a very simple one. There’s a single VCO, sweepable between saw and square waves, with controls for pitch, pitch modulation, pulse width and pulse‑width amount. There’s also a VCF — of the classic Moog ladder design, naturally — with cutoff, resonance and modulation, an LFO with controls for rate and waveform, and a four‑stage envelope going into a VCA.

Fairly straightforward so far, then, but there are a few small things that stand out as you study it more closely. For example, the modulation for pitch and filter cutoff is sweepable between the envelope generator and LFO, in which space are all sorts of unexpected and unconventional modulations. And the VCF Mod Amount control is bipolar, meaning that when you turn it clockwise from 12 o’clock the cutoff frequency goes up with the modulation and when you turn it anticlockwise it goes down. Simple enough, but it opens up a range of pleasing sound‑shaping possibilities. And then there’s the VCA Mode switch, which when switched on bypasses the envelope and sends a constant signal to the output — good news for drone enthusiasts and generally just very useful.

Beneath all this is a single octave of small rubber keys along with knobs for glide and keyboard scale. The keyboard is fine for triggering notes, but if your plans for the future include knocking out screaming multi‑octave prog solos, you may need to look elsewhere. The keyboard scale knob gives you one octave at its leftmost position, but increases the range as you turn it clockwise to a maximum of five octaves. Obviously this means the actual notes on the keyboard become meaningless as you increase the range, but it’s useful from an effects point of view.

Moving leftwards we reach the Utilities section and the patchbay, where things start to get even more interesting. For a start, there’s a wave folder. On a Moog... Probably someone reading this is thinking, ‘Actually, I think you’ll find the prototype Moog Centaur III from 1978 had two wave folders — and a low‑pass gate!’, but to everyone else this is a first. It’s not quite the dramatic clash between East and West Coast synthesis styles you might hope for, or the synth equivalent of the Berlin Wall coming down; it’s just a very economic way to add a lot more timbral variation — with just one socket and one knob you can coax sounds out of Mavis that no Moog synth has made before. For anyone who’s not come across it before, wave folding does exactly what it says on the tin — it folds waves. This means that the peaks of the waveform are folded back on themselves, creating interesting harmonics and, as you drive it harder, distortion. Essentially it can make very simple sounds into increasingly complex ones — and it also sounds wicked on drums. Mavis does this very well. And wave folding is not just limited to Mavis itself — plug any sound source into the Fold In socket on the patchbay and Mavis will merrily fold those waves as well.

The patchbay includes common or garden connections, like inputs for 1V/octave CV, gate, cutoff frequency, LFO rate, and outputs for the VCO, envelope, VCA and LFO. But mingling among them are a Sample & Hold output, a one‑into‑two multiple, an attenuator with accompanying control and a two‑channel mixer. Once you’ve finished trying to make R2‑D2 noises with the S&(ahem) this is a good point to get the included patch overlays out of the box and start to get a sense of what’s really on offer here. ‘Detuned Dual Square’ shows off the LFO’s credentials as audio‑rate (550Hz) oscillator; ‘Foldable Kick Drum’ showed me that what my puny attempt at a kick needed was wave folding; and ‘Who Needs A Sequencer’ probably needs no further explanation. It’s probably no coincidence that four of the five included patches (there are more available in the downloadable Mavis Exploration Patchbook) feature wave folding, underlining how well it fits into the Moog sonic toolkit. (Perhaps Moogs should always have had wave folders?) What the patches really show us, once again, is that there’s more to Mavis than meets the eye.

In Use

So, the Mavis is far deeper than it first appears to be, but what’s clever about this is that the learning curve is absolutely spot on. In fact it’s less of a curve and more of a ramp. It’s very simple to start with. You start off with some straightforward sounds, press the keys a bit and it’s all good. It’s that familiar Moog sound, the sound of a 24dB low‑pass ladder filter doing what it does and making everything sound rather lovely. Then you might muck around with the modulation a bit, sweep it between envelope and LFO control, see what’s what. Plug in a sequencer, get the envelope settings how you like them, maybe indulge in a bit of Berlin School repetition while tweaking the controls... It’s all very straightforward and it sounds good.

Fast forward a few days and there are patch cables everywhere, Mavis is wired into your modular in a way you only partially understand and you’re dimly aware that you lost two days when you plugged Mavis into Mutable Instruments’ Beads and everything went a bit more ambient than is strictly healthy.

The point is that the journey between bread‑and‑butter synth sounds and crazy sonic adventuring is a very smooth one. You experiment with some patching, maybe consult the manual a few times because it’s the sort of manual that’s worth consulting, and you just progress without even feeling like it’s happening. And you don’t have to go full modular to get a lot out of Mavis. There are a huge number of possibilities and subtle variation available with just the patchbay and the five cables included in the box — probably more than most of us will ever discover.


If there’s a phrase that sums up Moog’s recent adventures in semi‑modular, it’s probably ’deceptively simple’. The Mother‑32, for example, is capable of much more than a cursory glance at its front panel would suggest, and the DFAM is pretty much the definition of ‘greater than the sum of its parts’. It’s a similar story with the Mavis — what at first appears to be a very simple monosynth is actually capable of much more than you’d expect.

Moog have set out to make their synths more accessible without compromising on what they do, and they’ve succeeded.

Because of its size and price it’s tempting to place Mavis in the ‘toy’ category — a fun synth to mess around with but not a serious instrument. Yes, it is a fun synth to mess around with, but there’s a lot more to it than that. Firstly, it’s got that Moog sound. That familiar full‑fat analogue sound that’s so unmistakably Moog. It just sounds good. Then there’s the patchbay. Mavis is an unexpectedly versatile synth before you plug any cables in, but as soon as you start getting into patching it gets deep quickly — but not too quickly. Moog have designed three very successful semi‑modulars since the Werkstatt came out and the experience shows. Nothing is wasted and it’s clear that a great deal of thought has gone into the selection of controls and patch points. And that patchbay means that Mavis can play with other gear, be that another Moog semi‑modular or Sound Studio, or a Eurorack system or whatever. It can be added to an existing setup or even form the basis of a new one.

It would also be a great synth for a beginner, either at modular or synths in general; it’s simple enough to grasp but deep enough that it’ll be a long time before you outgrow it, if you ever do. Not that it’s just for beginners — there’s plenty here for the seasoned synth botherer. And then there’s the price...

In fact perhaps the best way to look at the Mavis is in economic terms (bear with me...). Firstly the economy of the controls and patch points, each one intelligently chosen and earning its place on a very elegantly designed instrument. And then, obviously tied into this, are the economics of cost. Moog have set out to make their synths more accessible without compromising on what they do, and they’ve succeeded. I’m not prepared to go on record as saying this is the cheapest Moog synth (‘The Moog Polythemus IV was only $11 at launch...’), but it’s certainly cheap for a Moog synth. And it’s an awful lot of synth for the money.  

Mavis Vs The Moog Sound Studio

Moog Sound Studio.

The Moog Sound Studio is a collection of Moog’s other semi‑modular systems and is available in three different bundles: DFAM + Mother‑32, DFAM + Subharmonicon, and the all‑singing, all‑bleeping DFAM + Mother‑32 + Subharmonicon mega bundle. All the individual instruments have been reviewed in SOS before, but briefly, the Mother‑32 is a single‑VCO analogue synth with a 32‑step sequencer, the Subharmonicon is basically Steve Reich in a Eurorack‑compatible box and the DFAM... Well, the DFAM is just bonkers, but in a good way.

The contents of the box, lovingly assembled in Moog’s factory in North Carolina.The contents of the box, lovingly assembled in Moog’s factory in North Carolina.The idea of the Moog Sound Studio, or Studios, is not just that they bundle together instruments designed to play nicely together, but also that they give you everything you need to create electronic music in one carefully curated box. Can a box be curated? Well, apparently, yes. Each bundle is thoughtfully put together with a four‑channel line mixer and power distribution hub (meaning you can run them all from one plug, and sum the instruments to a single output or a pair of headphones), a rack stand so you can mount them all together in a pleasing synth‑tower, a selection of colourful patch leads, a mood‑setting poster and an Eno‑esque patch inspiration card game. There’s also a lot of documentation — the MSS 3 comes with over 200 pages’ worth of manuals for the individual instruments, and the Exploration Patchbook which looks at using them all together. This is where the ‘curated’ bit really succeeds. Moog manuals are excellent. They are well written, beautifully produced and printed, and easy to understand. Moog’s manuals are so good, in fact, that their claim that someone who has never used a synth before could buy a Sound Studio and begin making music becomes plausible. You might look at the Subharmonicon or DFAM and think ‘I’m not sure these are the best synths for beginners,’ but the documentation is so good that anyone who’s prepared to put the time in could learn to use them and gain a pretty good overall grasp of subtractive synthesis while they were doing it.

Anyway, enough eulogising about manuals — what does Mavis bring to Moog’s semi‑modular party? The short answer is ‘really quite a lot’. Whilst more than happy to function as a standalone synth, Mavis has clearly been designed to complement Moog’s other semi‑modulars. The patchbay, for example, is now on the left‑hand side so that it can be placed patchbay to patchbay with MSS instruments and keep all of the leads out of the way of the front panels. And the combined 44+60 HP adds up to 104HP, a common Eurorack case size, inviting you to place the Mavis next to one of its siblings.

From a control point it’s almost as though they’ve looked at the existing instruments and added everything they thought was missing. After all, who hasn’t looked at a DFAM and idly thought, ‘Well yes, this is brilliant, but what if it had Sample & Hold, and an LFO, and an attenuator, and while we’re at it some mults...?’ This, by the way, is how you get sucked into modular... Before you know what’s happened you’ll be finding patch cables in your beard and last time you looked you didn’t even have a beard. By then it will be too late.

Of course, the Mavis gives you all of this functionality at a far lower cost than the Eurorack alternatives, and in a powered case to boot. That case, though, is possibly the only frustration in pairing Mavis with the MSS — that they don’t share the same form factor and can’t be piled on top to make an even bigger synth tower. This is undoubtedly because it would have pushed the Mavis into another price bracket (a Moog 60HP case on its own is around £90$90), but it would have been nice, wouldn’t it?

Aside from cost, the other reason why you might chose to add a Mavis to your MSS over Eurorack is that they’ve all been designed by the same engineers, and if you trust that Moog’s engineers know what they’re doing then you can probably safely assume that they’re going to work well together. And they do work well together. And yes, there is a lot of fun to be had modulating the Subharmonicon’s VCOs with attenuated S&H, or running the DFAM into Mavis’s wave folder, or pointing an extra LFO at the Mother‑32... You get the idea.

In short, Mavis adds to the MSS instruments as they add to one another, each multiplying the options available. The only down side is that it leaves you wanting more, and then we’re back at that slippery slope into modular again.


Like its semi‑modular brethren, the Mavis is Eurorack compatible. There’s a 10‑pin Eurorack power port on the PCB and it’s a matter of moments to unscrew the front panel from the supplied chassis and mount it in your rack. Mavis is 44HP wide and draws 175mA from the +12V rail. As such, Mavis can be added to an existing system as a complete synth voice plus some useful extras, or even form the basis of a new system, providing a lot of bang for a reasonable amount of buck for the would‑be modularist.


  • It’s an affordable Moog synth.
  • It’s a really very good affordable Moog synth.
  • Excellent gateway to modular.


  • Can’t be stacked with other Moog semi‑modulars to create a giant teetering synth tower.
  • Excellent gateway to modular!


The Mavis is an affordable and deceptively deep semi‑modular synth, and more than worthy of its Moog badge.