Review: Moog Subharmonicon

Subharmonics/ Undertones

Subharmonicon (Checkout Sunharmonicon in the Thomann shop) combines the terms Subharmonic and Rhythmicon. The latter is the name of one of the first electronic musical instruments, released in 1931 and is the quasi-forefather of drum computers. As with the Trautonium, which is one year older, the sound generation was based on subharmonics. These are undertones that are generated by dividing the frequency of an oscillator and can be mixed with the fundamental. In an inflexible form, this is known as the suboscillator in many classic analog synthesizers. Moog has taken up this concept and dressed it in a modern outfit. Two oscillators offer two subharmonics each and the pitch can be controlled separately, which qualifies Subharmonicon as a paraphonic synthesizer. The sonic result is sent through a classic Moog low pass filter and a VCA.

For Desktop or Eurorack

The Subharmonicon‘s technology sits in the same desktop enclosure as the Mother-32 and DFAM. The wooden side panels not only look chic, but also serve as a stand and provide a bevelled surface towards the user for better usability. Like the Mother-32 and DFAM, the Subharmonicon can be operated independently in a desktop case or screwed into a Eurorack case. The workmanship is flawless, the controls feel very expensive and offer a comfortable rotational resistance.

Pure Analog, No Storage

Similar to the DFAM, even experienced synthesizer programmers may need some time to get a feel for the sound generation when first touching the Subharmonicon. Beginners might even have difficulties getting a reasonable sound out of the synth at all.

The fully analog synthesizer does not have memory for recallable presets, but Moog has thought about this and included some preset sheets. These are cardboard templates that can be placed directly on the synthesizer thanks to cut-outs for the controls. Afterwards you can adjust the controls according to the markings and have a good starting point for your own creations. This is well thought-out because it makes getting started a lot easier.

Two Sequencers

Once you have memorized the sound generation and signal path, Subharmonicon is easier to understand. The user interface is divided into four sections. On the left is the sequencer section, which is not seen as a nice addition, but as an important part of the Subharmonicon‘s sound generation. There are two step sequencers with four steps each, whose values are adjusted by mini pots. Sequencer 1 changes the pitch of oscillator 1 or the frequency divider of the subharmonics derived from it, whereas sequencer 2 is pre-wired to oscillator 2.

Polyrhythmic

Four steps per sequence may not seem like much at first, but Moog has added a highly customizable polyrhythm option to the sequencer. Here, too, fixed dividers are used; four additional controls allow you to adjust the frequency of the sequencer. These four different rhythms can be assigned to Sequencer 1 and/or Sequencer 2 using two buttons each.

This sounds a bit confusing at first, but since all parameters are directly accessible, it‘s best to simply unscrew the screws and let yourself be surprised. Similar to the DFAM, the whole sequencer and sound generation concept is tailored to live performance; the synthesizer wants to be tried and played, and your head can remain switched off.

In the lower area there are still the controls for trigger and tempo adjustment. Unfortunately, it is not possible to save the sequences, since the sequencer is also analog.

Two Oscillators

The oscillator section is centrally located. Both oscillators are identical. They each offer sawtooth or rectangle waveforms as well as a mixed form with rectangle for the oscillator and sawtooth for the subharmonics. Pulse-width modulation is possible with Sub1, but the results are somewhat unusual because the Sub oscillates as a fast sawtooth.

The frequency of each VCO can be continuously adjusted with the large rotary control. The control range is 5 octaves, but can be limited to 3 or 1 octave by toggle switch. Quantize allows tuning beyond the usual 12 semitones per octave. If you want to experiment with only 8 semitones/ octave or a pure tuning, you are in the right place!

Four Subharmonics

Each oscillator has two subharmonics, whose frequency dividers can be individually adjusted. The subharmonics 1-16 are available for selection, so that harmonies and chords can be created with only one oscillator.

With three buttons, you can select whether the assigned sequencer should affect the oscillator or one of the subharmonics. In the lower section, the volume of the VCO and the two subs can be adjusted separately.

Moog Ladder Filter

This wall of sound from up to six oscillators enters the analog filter. The filter is a classic Moog 4-pole cascade filter. Unlike Mother-32 and DFAM, however, it can only be operated as a low-pass filter and not alternatively as a high-pass filter. Higher resonance values thin out the bass range, as is usual with Moog, so you can tame the power of four subharmonics a bit. At high resonance values, the Subharmonicon‘s filter goes into self-oscillation and can be used as a sound generator.

Rudimentary AD Envelopes

A dedicated AD envelope is available for filter modulation, with decay time down to a crisp five milliseconds. At the top, the control range for both attack and decay reaches up to 10 seconds, so that even longer sounds are no problem. Further modulation of the filter frequency is not directly provided for, but can be realized by using the patch panel, which allows good sounding filter FM when using the VCO outputs.

The amplifier also has its own envelope. Again, you will find only one decay control. We would have liked to have a separately adjustable decay time for some sounds. The envelopes are started by the sequencer, the manual trigger button, an external analog trigger or a MIDI signal.

Semimodular thanks to Patchbay

As usual in the series, the patchbay is arranged on the right side, so that no patch cables hang over the controls in a disruptive way. The patchbay offers 17 inputs and 15 outputs to modify the internal sound generation or to integrate external analog equipment. An external LFO can be looped in via the PWM input for the typical fat detuned sounds.

The oscillators can be isolated for further audio processing or as a modulation source (e.g. for the filter frequency). The two sequencer tracks can also be routed out to modulate other parameters, while there are separate inputs for each of the four rhythm generators. With the clock, reset and trigger connections, there are almost no limits to polyrhythmic fantasies when combined with a modular system.

MIDI Connection

Integrated into the patchbay is a MIDI input, which is still painfully missing on DFAM. A suitable adapter to DIN is included. MIDI signals can be used to trigger the envelopes and change the pitch of the oscillators. Unfortunately, the converted MIDI signal cannot be picked up by CV (e.g. to couple the filter frequency to the pitch). We also miss the transmission of pitchbend and modulation wheel MIDI controllers. At least Subharmonicon responds to some MIDI controllers, which you can use to automate the timing of envelopes in your DAW, among other things.