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Page 2: Moog Subharmonicon - EXCLUSIVE FULL REVIEW

Semi-modular Analogue Synthesizer By Gordon Reid
Published June 2020

But even this is not the Subharmonicon's greatest strength. Much as I usually decry using programming controls as performance controls (you'll never see any of my instruments with the paint worn away around the filter cutoff knob) the Subharmonicon is designed for this, and you'll not get the best from it unless you sweep the filter, tweak the resonance, modify the contours and do naughty things such as change the Rhythm assignments and press Reset and Next while it's playing. And, to prove that it's much more than just a bass sequencer (which I fear is almost all that it will be used for) I obtained some amazing sounds this way that included (don't laugh!) bird calls that were far beyond anything that I've ever obtained using more conventional synthesizers. Applying modulators generated by other modular synths extended the possibilities even further, and also had the benefit of being repeatable.

Racked up with the DFAM and Mother 32 in Moog's own three-tier stand.Racked up with the DFAM and Mother 32 in Moog's own three-tier stand.

If you have nothing but the Subharmonicon to hand — not even a MIDI keyboard, let alone something with CV, Gate and Trigger outputs — you can still play it by using the EG button to generate a permanent Gate and then setting the sequencers running. But it doesn't really come alive until you hook it up to patchable drum synths and other synthesizers. Then the fun really begins. Clearly, it has been designed to partner the Mother 32 and DFAM; the three sit very nicely alongside one another in Moog's dedicated stands and its manual even offers instructions on connecting and synchronising them. But if you prefer to mount it in a conventional Eurorack case that's no problem either. A standard 10-pin power header is provided and this derives all of the necessary power from the rack's +12V rail. However, note that the Subharmonicon draws 360mA, so make sure that you have sufficient headroom before installing it.

I reviewed the Subharmonicon some weeks before Moog announced it, and it performed faultlessly throughout. But, inevitably, there are some things that I would have considered doing differently. For example, it responds to just 11 MIDI CCs that control the partials' frequencies, the Attacks and Decays, and a weird bit of rhythm logic that controls how the sequencers step forward, plus two SysEx commands for switching Play on/off and determining the MIDI channel to which the unit responds. This means that it's unable to respond to pitch-bend or modulation, which might have added another level of expression. Apparently, this could appear in a future firmware update, so I hope that it does. I was also disappointed to find that there's no onboard portamento, although this can be achieved using an external slew generator. I would also have loved to see eight or even 16 steps, with the ability to modulate one sequence using the other to create longer melodies that could then be polyrhythmically mutilated. But since simplicity seems to be the aim here, I'm not going to moan. Well, not too much.

There's also one aspect of the sound engine that I would have done slightly differently. In common with many other synths' low-pass filters, increasing the resonance in the Subharmonicon's filter suppresses the low end. Since the basis of its sound generation is sub-harmonics, I think that a filter with somewhat less bass attenuation might have been a better choice. Moog's view, however, is that this helps to tame the low-frequency 'girth' of the sound which can otherwise become overpowering if all six sources are used in the bass register. To be fair, they have a point.


This is not a conventional analogue synth. It's an instrument designed for players who want to experiment with short but evolving sequences, and you'll either love it or wonder why Moog produced something that at first sight seems so limited. But while it won't appeal to everyone, I'm delighted that the company are willing to push the boundaries (even if that means pushing them back to 1930) to create something that reaches beyond the sounds and sequences that have pervaded popular music for the past half century. Some players are going to do amazing things with it.

But let me finish with a final, if only partially related, thought. Following the success of the Werkstatt and DFAM and now the appearance of the Subharmonicon, I wonder whether 2019's Engineering Workshop project, the Spectravox, will follow? I hope so... it seemed to be another rather interesting bit of kit. Time will tell.

What Are Sub-harmonics?

With the exception of an infinitely long sine wave, a cyclic waveform comprises numerous partials. If the sound is harmonic in nature, the second and higher partials are spaced at multiples of the fundamental frequency and are often called overtones. So if the note has a fundamental frequency of f, these overtones lie at 2f, 3f, 4f and so on. In contrast, sub-harmonics (sometimes called undertones) are defined not as multiples but as fractions of the fundamental frequency. So our note with frequency f has sub-harmonics at f/2, f/3, f/4 and so on. Some of these intervals are easily understood — for example, f/2, f/4, f/8 and f/16 are the first, second, third and fourth octaves below the fundamental. The sub-harmonics that lie between these fall at less obvious intervals and combinations of these can sound weird, wonderful or horrendous depending upon what you're trying to achieve.


The rear panel is extremely sparse, with just a single quarter-inch audio output that accepts a TS (unbalanced) audio plug or a TRS (two-channel) headphone plug, a socket for the universal wall-wart, and a Kensington security slot. As always, I have to criticise the thin cable coming from the PSU and the lack of stress relief. Come on Moog, you can do better! Note also that, when plugged in, the Subharmonicon is always switched on — there's no on/off switch.

In contrast, the top panel offers a patchbay that makes the Subharmonicon a semi-modular synth. Utilising 3.5mm sockets to maximise Eurorack compatibility, this offers 15 outputs that generate signals with ranges of 0-5 V, 0-8 V, 0-10 V, and ±5V as appropriate. There are also 17 inputs including a MIDI In, for which a five-pin DIN to 3.5mm adaptor cable is provided. The other 16 inputs typically expect signals to lie in the range ±5V and they use 1V/oct scaling where appropriate. Inserting plugs into inputs can either break the pre-patched connections or, depending upon function, see the external signals summed with the internal ones. Applying an external clock will override the internal clock, and a MIDI Clock will take precedence over both. Unfortunately, there is no pitch CV output derived from the MIDI input. Given the panel space available, this was a conscious decision and by all accounts a hard one for the developers, who viewed other I/O choices as of greater importance.

Joseph Who?

Joseph Schillinger was an influential music theorist, composer and teacher of composition who counted no lesser luminaries than George Gershwin, Glenn Miller and Benny Goodman among his students. With an interest in mathematics and early electronic music (he also collaborated with Léon Termen, perhaps better known as Leon Theremin, the inventor of the instrument that bears his name) Schillinger developed algorithms that embraced melody, harmony, rhythm and counterpoint to describe and compose music. Following his death, these were published as the Schillinger System of Musical Composition and another of his students founded a music school in Boston to teach it. This school later became the Berklee College of Music.


  • Everything about it is unusual — good unusual, not bad unusual.
  • Once grasped, it's great fun.
  • It sounds like a Moog — but a different flavour of Moog.
  • The results can belie the simplicity of its architecture.
  • It feels solid, robust and like a serious piece of kit.


  • There's no onboard portamento.
  • Currently, it doesn't respond to pitch-bend or modulation over MIDI.
  • There's no pitch CV derived from the MIDI input.
  • Applying filter resonance attenuates the bottom end a little too much for my taste.


The Subharmonicon offers a fascinating reinterpretation of two ideas revealed nearly a century ago, which have rarely been seen since. If you're interested in something that eschews conventional analogue synthesis and sequencing, and offers a different flavour of each, it should be high on your list of products to investigate.