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Moog Mother–32

Semi–modular Analogue Synthesizer
Published January 2016
By Gordon Reid

Moog Mother–32

Moog modulars have always been unattainable objects of desire for most of us. But all that’s about to change...

The AES Convention traditionally caters to the high end of the recording industry, so it’s not somewhere that you might expect to find a synthesizer company demonstrating their wares. But at the Los Angeles Convention in 2014, Moog raised more than a few eyebrows by exhibiting the Emerson Moog Modular, and probably had the busiest stand in the whole show, packed from the moment it opened until the security staff manhandled the star–struck knob–twiddlers out of the building. It was not a feat that I expected them to repeat in 2015, but they were there again a few weeks ago at the New York Convention, and a similar level of interest was being generated by the Mother–32: a semi–modular Eurorack synth/sequencer no larger than a couple of Emmo’s 5U modules. As a consequence, Moog’s small stand was again the busiest in the hall, proving, yet again, (if any proof were needed) that you can stick a Moog synthesizer of any size in front of even the most world–weary musos and sound engineers, and their knees go all a-quiver.

The Synth

The Mother–32’s primary sound source is a single oscillator that produces two waveforms, sawtooth and pulse, the latter with variable pulse width and PWM. Only one of the waveforms is available at any given time without the use of patch cables, but both can be obtained simultaneously via the patchbay. You can modulate either the VCO’s frequency or its pulse width using the internal LFO or contour generator but, again, you can affect both simultaneously by patching external sources to any of its three pitch CV inputs in the patchbay. Portamento is also available. A second sound source is provided in the form of an analogue white-noise generator, and you can mix the output from this with the output from the oscillator using the pre–patched voltage–controlled mixer. Alternatively, you can inject an external signal (or, for that matter, another internal one) at the external signal input, whereupon the noise source will be disconnected and the mix will be between the oscillator and the additional source.

The output from the mixer passes to the 24dB/octave resonant Moog ladder filter, which offers low–pass and high–pass modes. With a cutoff range that I measured to run from 17Hz to over 21.5kHz, the low–pass mode acts and sounds much as you would expect a Moog filter to act and sound, with or without resonance. In contrast, the high–pass response is anything but standard. If the resonance knob is in any position other than zero, it sounds similar to a peaking filter but, even without resonance, there’s still a great deal of signal passing at mid–frequencies, even at the highest cutoff frequency (at which very little audio should survive). However, you can patch the output from the VCF to the external audio input to create a feedback loop that generates something more akin to a conventional resonant high–pass filter response.

Despite these quirks, or maybe because of them, I rather warmed to this filter, perhaps because (in addition to the pre–patched modulation) both its cutoff frequency and its resonance can be controlled by CVs applied to the appropriate inputs in the patch bay. Voltage–controlled resonance is rare in small synths, so this is a welcome addition. Unfortunately, the filter doesn’t quite track at 1V/octave. I asked Moog why, and their product development specialist explained, “Because we used classic Moog analogue circuits, they would have to be trimmed for 1V/oct response. Each trimmer increases the price of the instrument, and we implemented just those that we believed were critical to the inter–connectivity of the instrument. But we still made sure that there were ways of achieving a 1V/oct response, either using an external attenuator or the Mother–32’s VC Mixer.” I tried this; it was a tad fiddly, but it worked.

The signal from the filter next passes to the VCA, which offers On (drone) and EG (contoured) modes. This feeds a single quarter–inch output on the rear panel which can be used for both line-level signals and headphones. It may sound trivial, but that’s a neat trick, accomplished using an output circuit that can drive high-fidelity signals successfully into both low– and high–impedance loads.

With so much going on on the front panel, the rear is understandably sparse, featuring just the quarter–inch audio output and a  socket for the 12V DC external power supply. With so much going on on the front panel, the rear is understandably sparse, featuring just the quarter–inch audio output and a socket for the 12V DC external power supply.

Unlike many modern synths, which marry an analogue signal path to digitally generated modulators and contour generators, the Mother–32’s LFO and EG are also analogue. The LFO offers triangle and square waves with a maximum range of around 0.1 to 600 Hz, again with simultaneous access to both waveforms via the patchbay. This means that it’s possible to use the LFO as a second oscillator, albeit (again) one that doesn’t quite track correctly when presented with a 1V/oct CV. You can overcome this using the same trick as with the filter, but it would have been nice if it had been designed to respond to 1V/oct from the start. The contour generator is a three-stage device offering AD and ASR modes, the first with multi–triggering, and the second with single triggering (legato). No specifications are quoted in the literature, but Moog told me that the range of attack times is nominally 1.25 to 3000 ms, while the range for the decay/release is nominally 1.25 to 7000 ms. The fastest rates are nice and snappy, but the slowest rates can’t give me the gentle sweeps that I sometimes want. You can overcome this by creating very low–frequency ramp, sawtooth and triangle waves using the sequencer (see the ‘Assignable Output’ box), but this requires much patching and programming to obtain something that perhaps should have been available in the first place.

The final module is a second voltage–controlled mixer. This isn’t pre–patched, so you have to insert cables to use it. If no cables are inserted in its inputs, it acts as a DC voltage generator, outputting 0V when the mix knob is at its anti–clockwise extreme, and +5V when it’s at its clockwise extreme. Alternatively, you can insert a signal into either its input 1 (which replaces the 0V at the anti-clockwise extreme), or its input 2 (which replaces the +5V at the clockwise extreme), or insert two signals and mix between them.

The Keyboard, Sequencer & MIDI

The largest section of the Mother–32’s manual is devoted to its miniature push–button keyboard and how you use it, together with some dedicated buttons, to program its digitally controlled, 32–step monophonic sequencer. But first things first — you can use the keyboard to play simple tunes. It spans just an octave but, with eight octave settings, you can use it to play across a huge range of pitches. You’re never going to attempt one of Rick Wakeman’s solos on it (nor would you ever want to) but it provides a convenient way to test sounds and program the sequencer, which is permanently connected to the VCO pitch, the Gate and the trigger for the contour generator.

To record a sequence, you simply enter record mode, play the desired notes on the keyboard or an attached MIDI controller, then exit and press Play, after which you can transpose the sequence into any key by pressing a note on the keyboard or the MIDI controller as it plays. You can also hold the sequence at a given step or return to the first step by pressing the appropriate buttons during playback. By default, the internal clock determines the tempo, but the Mother–32 also receives MIDI Clock (with the Tempo knob then acting as a clock divider) and it can respond to clock pulses and DIN Sync signals received at its Tempo CV input.

Things get a bit more complex when you start to adjust the gate duration for each note, adding rests, ties and mutes; adding accents (which accent both the VCF and VCA to emphasise notes when wanted), swing, portamento and ratcheting (repeating notes) on a step–by–step basis, either while recording, replaying or editing; and you’re soon going to become very intimate with the Shift button and the multi–coloured LEDs that help you to understand what’s going on. But there’s no rocket science here, and you’ll be making your sounds go round in circles in no time at all. Then, once you’ve created your masterpiece, you can save it to any of the 64 memories for later recall.

The Mother–32 offers much more in the sphere of MIDI performance and MIDI-CV conversion than you might expect. Most obviously, you can play it over a huge 10–octave range, with notes zero to 120 being converted to CVs ranging from –5 to +5 V. Both MIDI velocity and aftertouch are also recognised and, if set up appropriately, one (but only one at a time) can be made available as a ±5V CV at the Assignable output in the patchbay. This means that you can route velocity to destinations such as the filter cutoff frequency and output level, or aftertouch to (say) the modulation depth, brightness and loudness, making the Mother–32 a surprisingly powerful performance synth when played from a suitable MIDI controller. Other MIDI messages that can be translated into CVs are portamento time, portamento on/off, sustain, pitch–bend, modulation, breath controller, foot controller and volume. (See the ‘Assignable Output’ box.) In addition to all of this, you can use Program Change messages to select sequencer memories, and the Mother–32 will respond to MIDI Start/Stop/Continue messages, which means that it’s going to be far simpler to integrate it into a MIDI studio than you might imagine. Unfortunately, the lack of a MIDI Thru connector means that you’ll need a MIDI Thru box to control more than one Mother–32 simultaneously. This is a shame, as it would have been neat to be able to chain them, especially when mounted in the dedicated Moog racks. Also, the lack of a MIDI Out means that you can’t output sequences over MIDI. At the price, I’m not too concerned about this, but it’s worth noting nonetheless.

In Use

The manual contains nine example patches to help novices find their way around the synth and start to understand the basics of its programming, and it was while experimenting with these that I became aware of how confusing the Mother–32’s control panel might be for the beginner. The panels of most knobby synths are sub–divided into logical units such as oscillators, filters, and so on, but the Mother–32 makes no such concessions. On the other hand, there are just 14 knobs and nine switches defining a pre–patched sound, so I guess that you’ll soon find your way around.

If you think a  single unracked Mother–32 looks lonely, don’t worry: it’s a  more than capable synth by itself. If you think a single unracked Mother–32 looks lonely, don’t worry: it’s a more than capable synth by itself. My next job was to create some of my own sounds on a single Mother-32. Initially restricting myself to using just the VCO and noise generator as sound sources and to using the filter in its LP mode, I was very pleasantly surprised by the quality and depth of the lead and bass sounds I obtained, especially with judicious use of PWM to thicken things up a bit. Mixing the sawtooth and PWM waves improved things still further and, when I played the results through a Space Echo, I quickly obtained sounds — sometimes smooth and beguiling, sometimes raw or downright aggressive — that I would be happy to use on serious projects. However, modulation and contouring are not the Mother–32’s greatest strengths even if you invoke the sequencer’s ramp, saw, triangle and random modes, and the lack of an ADSR made it hard for me to obtain the quasi–orchestral sounds I wanted, so this probably isn’t going to be the Mother–32’s forté.

I next created a range of sound effects and industrial noises. The Mother–32 excels at these, especially when the VCA is locked On to permit drones and external signal processing. People who use synths in ways that don’t involve playing widdly lines on a keyboard are going to appreciate this. Then I invoked the sequencer. Given the limited number of controls — a single row of eight buttons to represent up to 32 steps, each with its own pitch CV, gate length, slew, ratchetting and accent — I was surprised by the ease with which I could create, edit and use my sequences. If I’m honest, I made numerous programming mistakes because I hadn’t performed the right combination of key presses and knob turns in the right order with respect to other arcane combinations of key presses and knob turns, but if you’re a fan of serendipity — and I suspect that the vast majority of purchasers will be — you’re going to love it.

Now it was time to mount the three Mother–32s into the rack supplied for the review. At first, I was unable to do so, because forcing them in would have meant denting the wooden cheeks where they butt together, so I relayed this information to Moog and, the following day, a replacement rack arrived. The mounting holes in this one offered a fraction of a millimetre more ‘play’ and everything now fitted perfectly. The resulting setup was an incongruous mixture of tiny and huge: if it were four foot tall it wouldn’t look wrong, but you can fit it into a reasonably sized shopping bag! That’s not to say that the Mother–32 is lightweight; despite a move to modern electronics and manufacturing techniques, it’s chunky and robust, and the reassuring solidity of the knobs and the quality of the 3.5mm sockets put some other Eurorack modules to shame.

I then spent many happy days experimenting with the ‘Mother–96’, as I had dubbed it. I started by patching it as a three–oscillator monosynth, playing the topmost one using MIDI and the others using CVs derived from the first. I could now create fiendishly complex sounds because I had three resonant filters, three (albeit limited) contour generators, three LFOs, and six voltage–controlled mixers at my disposal. Moving on, I then used all three of the synths’ MIDI inputs so that I could extract a different MIDI message from each, making the Mother–96 both velocity- and aftertouch-sensitive, while simultaneously responding to a third MIDI message of my choice. Then there were the endless opportunities for all manner of AM and FM sounds (although not for oscillator sync, which isn’t provided). As for programming the three sequencers and sync’ing them to one another (or not), the possibilities were enormous, whether used conventionally or by cross–patching them to create chaotic rhythmic sounds and sequences. To be honest, I found the number of shifted functions in the sequencer to be a little irksome but, given the size of the panel, it was either this or lose facilities. I also found the patchbays to be a bit fiddly when heavily patched, but that’s an inevitable consequence of the size of the synth. If you want a combination of small, light, portable, and flexible with decent-sized knobs and no menus, you’re going to have shifted functions, tightly packed controls, and even tighter-packed sockets. Live with it.

It was while doing this that I discovered the limitations imposed by the usual dearth of multiples, and I soon found myself grabbing a large box of long patch cables (the synth comes with just five short ones) and hooking the Mother–96 up to the multiples in my Analogue Systems RS Integrator. A couple of hours later, I noticed that, without being aware of having made the decision, I had also used some of the Integrator’s VCAs, mixers, and more esoteric control modules to extend the Mother–96’s capabilities. Had I wanted to make this integration (no pun intended) more permanent, I could have mounted one or more of the Mother–32s within the Analogue Systems cases, using their 10–pin headers to connect to the AS power supplies. (To later return the synths to their Moog cases, I could then have reversed the operation, although, as I discovered when I removed one out of curiosity, remounting them is a bit fiddly because Moog’s cases use individual eyes for the screws, not rails.) Alternatively, I can imagine many of Moog’s forthcoming 104HP cases being populated with a Mother–32, a suitable power distributor, and a range of other manufacturers’ modules.

The Mother–32’s front panel measures 319 x 107 mm, which in Eurorack terms amounts to 60HP.The Mother–32’s front panel measures 319 x 107 mm, which in Eurorack terms amounts to 60HP.At no time during the review did I need to calibrate any of the three Mother–32s. I just switched them on and, after a short warm–up period, they were ready. Nevertheless, I was pleased to see that Moog provide a small adjustment tool and instructions that should allow anyone to tune and scale them if necessary. You can access the four trimmers — VCO offset, frequency control gain, external 1V/oct gain,and KB CV gain — through small holes in the control panel but, as already mentioned, there’s no means for the user to adjust the filter or LFO tracking in this way.

Ultimately, there’s little else to criticise about the Mother–32. Sure, it would be nice to be able to chain the power for multiple units mounted in one of Moog’s racks, but that would have added to the cost and is for that reason forgivable. Likewise, cost probably precluded the MIDI Thru and MIDI Out that I would have liked to have seen included. In the end, I encountered just one issue that manifested itself in two of the Mother–32s I tested. A tiny bit of LFO was leaking into the VCO’s pitch CV, and nothing I could do would eradicate it. I contacted Moog’s technical people, and it turned out that this was a known issue confined to a handful of early units and long since corrected. The third unit that I had was fine in this regard, as will be any that you now purchase. If by chance you encounter one that exhibits this behaviour, Moog will correct it.

Final Thoughts

At the AES Convention, I asked Moog’s Product Marketing Manager, Trent Thompson, why the company had finally decided to enter the Eurorack arena, and why their first product was an integrated synth. “By revisiting our larger 5U modules and re–learning how we had done things in the past, we were also able to determine how to make modular synths smaller and more accessible,” he told me, “so we set ourselves the goal of designing a small, patchable synthesizer that anyone could explore and enjoy. Many musicians are curious about the Eurorack format, but they are also intimidated by it, so, when designing the Mother–32, we decided to make expansion a choice rather than a requirement.”

When put like this, it seems eminently sensible and, if some experienced Eurorack enthusiasts choose to view the Mother–32 as a bit basic, they’re missing the point. It’s a surprisingly versatile synthesizer that retains the elusive ‘Moog–y’ sound, and its fully integrated sequencer takes it way beyond ‘Moog does Eurorack’. There are alternatives of course, but nothing I can recall that offers the same, slightly ambiguous combination of simplicity, complexity and flexibility at the price. I’m therefore not surprised that it has captured the collective imagination of the analogue synth community, to the extent that there was even a rumour floating around that Moog had received advance orders for 8000 units. When I asked Thompson about this, he was understandably reserved, but he admitted that, “We’ve been overwhelmed by the number of orders we’ve received, so we’re increasing our production capacity, adding new people, and building Mother–32s as fast as we can to fulfil the orders.”

Consequently, I suspect that the Mother–32 may prove to be Moog’s most popular synth yet. It’s also going to attract new users to the format, and could even expand the market for the established Eurorack manufacturers, hopefully leading to additional money floating around for further developments in an upward spiral of product releases and musical possibilities. Whether you’re interested in dipping your toes into the Eurorack arena, or are looking to expand an existing system, you shouldn’t ignore it.  

The Assignable Output

You have to press an arcane combination of buttons to access the Mother-32’s Setup mode, but at least this ensures that you’ll never enter it by accident. Once there, you can determine the received MIDI channel (1–16), the Tempo input mode, and the nature of the CV available from the Assignable output. There are 16 of these CVs, nine generated by the sequencer and seven derived from incoming MIDI messages, although only one can be used at any given time.

Sequencer messages

Output

Accent (Default)

+5V pulse on Accented steps.

Clock

+5V Clock at the tempo.

Clock /2

+5V Clock at half the tempo.

Clock /4

+5V Clock at one quarter the tempo.

Step Ramp

–5 to +5 V ramp that increases across the pattern and resets on step 1.

Step Saw

+5 to –5 V sawtooth that decreases across the pattern and resets on step 1.

Step Triangle

Alternates the ramp and sawtooth responses on alternate loops.

Step Random

A random voltage on each step.

Step 1 Trigger Output

+5V pulse on step 1 of the pattern.

MIDI messages

Output

Velocity

Channel Aftertouch

Pitch-bend

CC1 (modulation)

All –5 to +5 V CVs derived from MIDI values 0 to 127.

CC2 (breath controller)

CC4 (foot controller)

CC7 (volume)

The Patchbay

The term semi–modular is used to describe synths in which a fixed complement of modules are pre–patched internally so that you can create sounds without using cables, but which also allow you to connect their constituent parts in novel ways using patch cables. The Korg MS20 and the ARP 2600 are famous examples of this genre, although it’s to the ARP that the Mother–32 is more closely related.

The patchbay on the Mother–32 is sensibly placed to one side of the synth so that you can reach the knobs and switches without having to squeeze your fingers between cables. To help you to identify what does what, those sockets with plain legends are inputs, those with text in boxes are outputs, and those with white circles around the retaining nuts are Gate inputs.

 

Inputs:

Outputs:

External Audio

VCA

Mix CV

Noise

VCA CV

VCF

VCF Cutoff

VCO Saw

VCF Resonance

VCO Pulse

VCO 1V/octave

LFO Triangle

VCO Linear FM

LFO Square

VCO Modulation

VC Mix

LFO Rate

Mult 1

Mix 1

Mult 2

Mix 2

Assign

VC Mix Control

EG

Mult

KB

Gate

Gate

Tempo

Run/Stop

Reset

Hold

Specifications

VCO waveforms

Sawtooth and pulse, the latter with PWM.

VCO range

1V/oct from 8Hz to 8kHz, maximum frequency ~ 16kHz.

Portamento

Yes.

Noise generator

White.

Voltage controlled mixer 1

Mix between VCO and noise/external signal.

VCF

Resonant 24dB/oct switchable low/high-pass, 20Hz to 20kHz.

Audio VCA modes

On/contoured.

LFO waveforms

Triangle and square.

LFO range

0.1 to 600 Hz.

Contour generator

Switchable AD/ASR.

Voltage-controlled mixer 2

Two channels, externally patched.

Multiple

One-in/two-out, buffered.

Keyboard

13 buttons with eight octave settings.

Sequencer

32–step, 64 memories.

Patch bay

32 connections (3.5mm).

Audio output

Quarter–inch TRS, combined line-level and headphones.

Dimensions

Eurorack 60HP, 26mm deep. Case size 319 x 107 x 132 mm.

Weight

1.6kg.

Power supply

Universal wall-wart: input 100–250 V AC, 50–60 Hz, output 12V DC, max 1A.

Current draw

Maximum 230mA.

Published January 2016