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Moog Grandmother

Semi-modular Analogue Synthesizer
Published September 2018
By Gordon Reid

‘What a big front panel you have, Grandma’ — the Grandmother measures 55 x 36 x 14cm. And granny’s no lightweight either, weighing in at a substantial 7.25kg.‘What a big front panel you have, Grandma’ — the Grandmother measures 55 x 36 x 14cm. And granny’s no lightweight either, weighing in at a substantial 7.25kg.

Don’t be misled by the colourful panel and eccentric name — the Moog Grandmother is a serious and capable synthesizer.

As a keyboard-based semi-modular synth, the Grandmother is a new departure for Moog Music. Nonetheless, many of its innards are based upon pre-existing Moog technology, some from the 1960s and 1970s, and some more recent. Physically, it’s contained in a surprisingly sturdy case that isn’t just reminiscent of the Realistic MG-1 (which was designed by Moog Music in the late 1970s), it’s an almost exact recreation, albeit a couple of inches wider and deeper than the earlier model.

Musically, a great deal can be achieved using the Grandmother without patch cables, although the possibilities increase hugely when you start to patch it because this allows you to create all manner of new audio and control signal paths that greatly extend its capabilities. What’s more, it almost begs to be placed in front of a panel of Eurorack modules and, when I did this, it sprang to life in a way that... but now I’m getting ahead of myself. So let’s start, in the usual fashion, by looking at the technology within the Grandmother itself.

Synthesis

Moog’s web site states that the Grandmother’s dual oscillators are derived from the Minimoog’s. Given their sound and the facilities on offer, this seems a little odd, so I asked for more information and it transpired that they are based upon the oscillators from the Minimoog Voyager, not the original Minimoog or the more recent Model D. Each offers four waveforms; triangle, sawtooth, square, and a pulse that I measured to have a duty cycle of about 16 percent (osc 1) and 18 percent (osc 2) rather than the 25 percent stated in the manual, with both the square and the pulse waves offering PWM. Footages are restricted to 32’ up to 4’ for osc 1, and 16’ up to 2’ for osc 2, although osc 2 can also be detuned by up to ±24 semitones, allowing you to create all of the usual sounds and effects. Each of the oscillators offers a pitch control input socket, and any CV applied here is added to that generated by the keyboard, which is as it should be. In addition, each offers a direct output. The third socket in each oscillator section differs between the two. On osc 1, it’s a PWM input that allows you to sweep the pulse width using CVs other than those generated in the modulation section. On osc 2, it’s a linear FM input that allows you to generate bell-like and other enharmonic timbres. Finally, a big red button offers hard sync of osc 2 and, with appropriate patching, all of the usual sync sounds are obtainable.

Unless patched otherwise, the mixer is the next stage in the signal path, and this offers hardwired inputs for osc 1, osc 2 and a white-noise generator, all of which can be replaced using the appropriate signal input sockets. It’s based upon a vintage device called the Moog CP3 and is capable of mixing audio signals, control voltages, or even a combination of the two. It has a number of characteristics that may have seemed like flaws at the time, but which are now deemed desirable. Most obviously, signals distort at input levels above 12 o’clock or thereabouts, often reinforcing the fundamental frequency or adding a gentle high-end fizz. Also, due to a lack of headroom, increasing the gain of any one of the inputs can suppress the signals presented to the others, which can be viewed as a defect or as a sound sculpting facility as you choose.

The signal now passes to the 24dB/oct ladder filter. This is again based upon a vintage device — the Moog 904a found in modular systems such as the Moog IIIc and System 55. Using the knob alone, the maximum cutoff frequency is around 11kHz but, once you apply suitable CVs, this soars to over 20kHz. Its sound is quite unlike that of the Minimoog filter, not least because resonance is maintained across the whole of the cutoff frequency range. As well as offering a hard-wired bi-polar response to the contour generator, it responds to keyboard tracking rates of 0, 50 and 100 percent and, when oscillating, it’s possible to play it in tune across the whole keyboard range. Doing so, I accidentally recreated the introduction from ELP’s ‘The Endless Enigma’, which was a pleasant surprise. It also offers three patchable inputs and a patchable output. The inputs comprise an audio signal input that replaces the hard-wired input from the mixer, a contour amount input, and a cutoff frequency input, the last of which allows you to create audio-frequency filter modulation, which is always fun.

Following the filter, the output section comprises a VCA based upon the Moog 902, followed by a six-inch spring reverb based upon the Moog 905, and finally a volume control. The VCA offers three gating options: Env (the VCA is controlled by the contour generator), Keyboard Release (the VCA gain has instant attack, full sustain level, and a release time determined by the Release setting of the contour generator), and Drone (which holds the VCA open). A CV input extends this functionality still further and you can obtain AM synthesis effects using this. You can also inject an alternative audio signal into the VCA using the VCA In socket, which disconnects the hard-wired output from the low-pass filter section.

I was happy to find that the reverb is largely immune to impacts — you have to give the Grandmother a decent punch to get it to go ‘boing’ — but, unfortunately, it shares a shortcoming with all unmodified 905s; the Mix knob ranges from 100 percent dry at one extreme to 100 percent wet at the other. When recreating the Emerson Moog Modular some years ago, Gene Stopp and Brian Kehew found that the classic Moog reverb sound was obtained when the dry signal was allowed to pass unhindered and the Mix knob determined how much reverb was added to this, and it would have been nice had the Grandmother adopted the same functionality. You can use the Reverb In socket to disconnect the reverb from the pre-patched signal path, and its independent output on the rear panel means that you can patch it anywhere you like in the signal path, or even use it as an independent signal processor.

The Grandmother’s modulation section is based upon an oscillator with a wider frequency range than you might expect, ranging (unpatched) from 0.07Hz to 1.3kHz, which suggests all manner of FM and AM possibilities. If you direct the KB Out CV to the modulation Rate In, you can push the frequency even higher and even play the modulator like a conventional oscillator. With suitable settings, I was able to force it up to more that 20kHz, so I can see why Moog call it a modulator rather than an LFO. In addition to its Rate knob, it offers four further knobs that determine its waveform (sine, sawtooth, ramp and square waves) and the maximum amount of modulation applied to each of the oscillators’ pitches, the oscillators’ PWM amounts, and the filter cutoff frequency. Another CV input, Sync, works in the same way as sync on a conventional audio frequency oscillator. Finally, there are two outputs, one carrying the generated signal and the other carrying a S&H signal derived from the noise generator at the modulation rate.

The ADSR contour generator is a simpler device based upon the Moog 911 module, although it offers an unusual configuration with knobs for the A, D and R (timing) parameters and a large slider for the S (level) parameter. This is either a pointless affectation, or it makes a weird kind of sense. It offers a trigger input and two outputs, one with positive and the other with negative polarity.

The final synthesis section is called Utilities and, in addition to a passive four-way multiple, this offers two further devices that have to be patched to be used: a 6dB/octave high-pass filter and a bi-polar attenuator. Neither of these offers voltage control, so the filter is static and the attenuator can’t be used as a VCA although, with nothing patched to its input, it can be used as a DC voltage source.

Performance

The controller panel to the left of the keybed contains a sprung pitch-bend wheel and a mod wheel that controls the amount of modulation applied through the hard-wired mod paths. The second of these was miscalibrated when I received the review unit, but running a tiny SysEx file supplied by Moog fixed this and all was then as it should be. This panel also contains the knob for the portamento (glide) rate. Surprisingly, the Global settings allow you to choose between linear constant time, linear constant rate, and exponential glide modes and, if you press the Shift button while adjusting the rate, you can turn legato portamento on and off. So that’s six types of portamento!

Moog Grandmother

The three buttons in this section also allow you to shift the keyboard up and down in steps of one octave, as well as providing much of the control needed for the arpeggiator and sequencer. The arpeggiator itself is a simple one, offering ‘as played’, forward/backward, and random modes repeated over one, two or three octaves, with a Hold function that allows you to release the keys if you need your hand for something else. As you would expect, the Rate knob determines the arpeggio rate or, if an external clock or tap tempo is used, it selects the ppqn ratio used.

The sequencer is a more powerful beastie, capable of storing up to three non-volatile monophonic sequences of up to 256 notes each. Creating a sequence is simple; set the Mode to Rec and choose which sequence to record, then play the notes, add rests, add ties, and program legato transitions. Accents can also be programmed, and these generate a dedicated AR contour CV that you can direct from the KB Vel output to destinations of your choice. There are again three playback modes, and you can transpose the sequence during playback. You can even edit sequences during playback although, as I discovered to my chagrin, attempting this while in the wrong mode erases the whole sequence.

Creating Sounds

To evaluate the Grandmother further, I programmed some standard patches using only the internal connections. Doing so, I quickly came to appreciate the choice of oscillator because, while some people find vintage oscillators to be loose and animated, for others that’s just another way of saying they’re unstable and prone to drift. Does this mean that the Grandmother’s are any the less powerful for being more stable? In my view, no, and I was impressed by their brightness, the cross-mod sounds that I could obtain, and their interaction with the filter. As for the filter itself, I liked many aspects of this, although I prefer those that don’t attenuate the bottom end quite so much when the resonance is cranked up. I also made frequent use of the spring reverb, not as a final effect but as part of the sound design process.

Next, it was time to start experimenting with patch cables, and my first test was to see whether I could use the modulator as a third audio-frequency oscillator. This proved to be simple, and I was able to create an amazing range of three-oscillator sounds that emulated Moog’s modular synths. Hearing Keith Emerson’s I/III/V and I/IV/V patches emanating from such a small synthesizer was seriously impressive. Much joy followed, especially when I discovered that looping the Eurorack audio output back into the mixer has a similar effect as creating an external loop on a Minimoog, adding significant depth and welly to the sounds.

So far, I’ve barely mentioned the CV outputs at the top of the Arp/Seq panel, but these became three of the most used facilities in my patches. The first is a Gate Out, which outputs a keyboard gate or, when using the arpeggiator or sequencer, a gate for each note generated. The next is marked KB Out, and this outputs the pitch CV generated by the keyboard, the arpeggiator or the sequencer. Finally, there’s KB Vel Out, which outputs the keyboard velocity CV or, in arpeggiator mode, the velocities of the notes used to generate the arpeggio. Whoo-hoo! — the 32-note keyboard generates velocity messages, transmitted as both analogue CVs and MIDI messages, As you might imagine, I had the KB Vel Out directed to the VCF Cutoff In and the VCA Amt In pretty much throughout this review. Unfortunately, while low-note, high-note and last-note key priorities are available, the Grandmother offers only single triggering, which is an unexpected oversight. I quizzed Moog about this, and was told that it’s on the list for a future update. Fingers crossed.

Before finishing, I added a five-octave MIDI keyboard into the equation and placed the Grandmother in front of my Analogue Systems Integrator. That’s when things got REALLY interesting. Perhaps because of its colour scheme, there’s a temptation to view it as a beginners’ synth, but that’s not the case, and it offers huge potential for players who are prepared to make it jump through hoops that no entry-level instrument ever could. Connecting it to basic modules such as additional mixers, multiples and VCAs was great; exploiting additional contour generators and esoteric modules such as clock dividers, frequency shifters and additional filter banks was even better.

Conclusions

Moog describe the Grandmother as “a sonic playground” on which the journey of discovery is as important as the end result. I’m normally critical of such hyperbole, but I must admit that I spent a great deal of time experimenting with it ‘just to see what happened’. I found it to be a surprisingly capable instrument, especially when you take advantage of its patching capabilities and, although the dearth of mixers, multiples, contour generators and VCAs places constraints upon what you can achieve on it in isolation, it’s completely at home at the centre of a small modular setup where it can be used as both a controller and as a powerful sound source.

And what of the price? Moog Music have been broadening their low-cost range in recent years and, while retaining their reputation as the manufacturer of expensive Minimoogs and hyper-expensive modular synths, they now offer several sub-£$1000 instruments. While the Werkstatt-01, the Mother-32, the Minitaur and the Sub Phatty have their places, I’m convinced that the Grandmother offers the best ‘bang for the buck’ of any of these. Indeed, I can’t see how you could assemble the same set of facilities elsewhere for anything close to the price. Of course, if it had a wider keyboard and a few more modules... well, that would be even grander, and maybe Moog will consider this for the future. But in the meantime we can all enjoy the thought of people selling their synthesizers for a new Grandmother.  

The Rear Panel

Rear panel of the Moog Grandmother.Rear panel of the Moog Grandmother.

The Grandmother offers a more interesting rear panel than you might expect. Alongside the Fine Tune knob there are three audio outputs: a quarter-inch socket that accepts unbalanced (TS) plugs for line level connections and stereo (TRS) plugs for headphones, a 3.5mm socket that outputs the audio in the standard Eurorack range of ±5V, and a 3.5mm socket that carries the output from the spring reverb. There’s also a high-gain quarter-inch signal input that injects audio directly into the mixer which, amongst other things, allows you to use the Grandmother as an external signal processor. Next to these, there’s a panel that augments the Arp/Seq section. This comprises a clock input that can act as a conventional clock or a step trigger, a Start/Stop input, a Reset, and an internal clock output. The final panel comprises five-pin DIN MIDI in/out/thru sockets, as well as MIDI in and out via USB.

Unfortunately, alongside all of this goodness there’s the power input, which is a simple barrel connector for an external 12VDC ‘snake that swallowed a wombat’ PSU. There’s no locking connector nor even, despite the promise in the manual, a stress relief hook, which means that it’s going to be far too easy to disconnect the power accidentally. Come on Moog, this isn’t good enough!

More Than An Analogue Synth?

When the Grandmother arrived, one note (a low F) played a pitch a little flat of the Bb above it. It wasn’t a physical fault because the error moved up and down the keyboard when I shifted the octave, and playing the self-oscillating filter didn’t exhibit the same behaviour. Clearly, there was a glitch in the digital electronics that interpret the pitch, and a quick email exchange with Moog Music revealed an undocumented calibration/reset command that sorted things out.

But this raised some questions in my mind about the role of the digital electronics in the synth and, when I studied its Global parameters and the surprisingly extensive list of MIDI functions, I noticed that some MIDI CCs are capable of altering the sound itself — things such as the oscillators’ octave settings, the osc 2 detune amount and the LFO rate. Another surprise was its ability to respond to a sustain pedal over MIDI, all of which suggests that — despite the lack of ADCs, DACs and patch memories — there’s rather more going on behind the Grandmother’s knobs than meets the eye.

What’s In A Name?

There are many things that Moog do well, but naming synths isn’t one of them. The whole ‘Phatty’ thing may have seemed clever when it was conceived, but it was far from the company’s finest hour. Now we have the Grandmother. When I first heard the name, I was aghast. To me, a Moog synthesizer should evince power and excitement, not frail old ladies smelling of lavender.

The chaps at Moog explained it to me thus; if previous Moog monosynths were ‘the mothers of all synthesizers’, this one is even ‘grander than a mother’. Unfortunately, while the phrase ‘the mother of...’ has become popular in the USA in the past few years, it means little or nothing to the other 95 percent of the world. What’s more, it’s a term that was popularised by Saddam Hussein, promising “the mother of all battles” before the first Gulf War. Oops!

Published September 2018