Rhythmicon
Documentation
Module for VCV Rack 2 and Max for Live devices for Ableton Live 12. Last updated 19 October 2026.
Module · VCV Rack 2 · 36 HP · €15
A polyrhythmic sequencer
Four rhythms divide one clock, two four-step sequencers follow them, and the patterns drift against each other until they meet again on the one. Every step plays its note together with two undertones.
Max for Live · Live 12 · Rhythmicon €9 · Rhythmicon+ €27
A polyrhythmic sequencer, with or without its own sound
Four rhythms divide one clock, two four-step sequencers follow them, and the patterns drift against each other until they meet again on the one. Every step plays its note together with two undertones.
There are two devices. Rhythmicon is a MIDI effect: it plays any instrument or Drum Rack on its track. Rhythmicon+ is an instrument with its own sound: two oscillator systems with exact undertones, a four-pole ladder filter and a Destroy page. The sequencer is the same in both; this manual says where they differ.
The idea goes back to 1931. Henry Cowell asked Léon Theremin to build an instrument that turns the overtone series into rhythm: one pulse per bar, two, three, up to sixteen. Rhythmicon brings this together with the undertone series, the mirror of the overtones, the way Moog's Subharmonicon does. It is our own design, with a display that shows the polyrhythm, accents, swing, density and 16 scales.
Install
After the purchase, open your Thoow downloads and pick your system: Mac (Apple Silicon or Intel), Windows or Linux. Close Rack, put the .vcvplugin file into Rack's plugins folder (in Rack: Help → Open user folder) and start Rack again. Rhythmicon appears under Thoow. For an update, delete the old ThoowRhythmicon folder first.
After the purchase, open your Thoow downloads and save the .amxd file. You need Ableton Live 12 with Max for Live (Live 12 Suite, or Live 12 Standard with the Max for Live add-on), on Mac or Windows.
- Rhythmicon (MIDI effect): drag it onto a MIDI track in front of an instrument or a Drum Rack.
- Rhythmicon+ (instrument): drag it onto an empty MIDI track. It needs no MIDI clip.
Both play with Live's transport: press play and they run in time with your set. Drop the file into your User Library to keep it at hand.
How it works
Everything starts from one clock that ticks in sixteenth notes. Each of the four rhythms divides it by a number from 1 to 16: ÷4 hits on every beat, ÷3 every three sixteenths, ÷7 every seven. Each rhythm drives sequencer 1, sequencer 2, both or none.
A sequencer has four steps and moves on by one step whenever one of its rhythms hits. Two rhythms on the same sequencer make an uneven, swinging line; if they hit at the same moment, the sequencer moves only once. The other sequencer drifts at its own pace.
The whole pattern repeats when all rhythms that drive a sequencer meet again on the same tick: the least common multiple of their divisions. ÷4, ÷3, ÷5 and ÷7 meet again after 420 sixteenths. The display counts this cycle: CYCLE 17 / 420.
Each step plays a note and two undertones: the frequency of the note divided by 2 to 16. ÷2 is one octave down, ÷3 an octave and a fifth, ÷5 two octaves and a slightly low major third. So rhythm and chord grow out of the same numbers.
Rhythms
| Control | Range | What it does |
|---|---|---|
| ÷ 1 … ÷ 4 | 1–16 | Divides the clock for this rhythm. Factory setting ÷4, ÷3, ÷5, ÷7. |
| SEQ 1 · SEQ 2 | on / off | The two buttons under each rhythm: lit = this rhythm drives sequencer 1 or 2. A rhythm without a button still sends its gate at its ÷ output. |
| DENSITY | 0–100 % | Leaves out hits, see Swing and Density. |
The left part of the device has one row per rhythm: the ÷ number (1–16, drag or type), a lane with the hits of the current bar, and the buttons 1 and 2: lit = this rhythm drives sequencer 1 or 2. Factory setting ÷4, ÷3, ÷5, ÷7, the first two driving one sequencer each.
Sequencers
| Control | Range | What it does |
|---|---|---|
| STEP 1 … 4 | ±1 octave | Pitch of each step above or below PITCH. RANGE widens it to ±2 or ±5 octaves. With a scale, every step snaps to it, and the display shows its note. |
| ACCENT | on / off | The buttons under the steps: an accented step sends 10 V at ACC while its gate is open. Factory setting: step 1. |
| PITCH | ±24 semitones | Base pitch of the sequencer around C4. Factory setting −12, C3. TR 1 / TR 2 add a V/OCT transposition. |
| SUB 1 ÷, SUB 2 ÷ | 1–16 | The two undertones of this sequencer, see Undertones and Moves. |
In the middle, each sequencer has one row of four step fields. The tabs Steps and Voices switch what the rows show.
| Control | Range | What it does |
|---|---|---|
| Step field | ±100 % | Drag up or down to set the pitch of the step; the field shows the note. 100 % is the full Range above PITCH (±1, ±2 or ±5 octaves). |
| acc | on / off | Accent under each step: a harder note (velocity 127 instead of 92). Rhythmicon+ plays accented steps louder. |
| Pitch | −36 … +24 | Base pitch of the sequencer in semitones around C4. Factory setting −12, C3. |
The playing step lights up. Every control is a Live parameter: automate it, map it to a controller or let Thoow Motion move it.
Undertones and Moves
Each sequencer has three voices: the note, Sub 1 and Sub 2. A sub is the note's frequency divided by a whole number from 1 to 16. Factory setting ÷2 and ÷3: one octave and an octave plus a fifth below. Higher numbers go deeper and further away from the piano keys; ÷5, ÷7 and ÷11 sit between them, and that is the sound of it.
Moves decides per voice whether it follows the steps. On: the voice plays the step pitches. Off: it stays on PITCH and drones under the moving voices. Turn off the note and the subs walk below it, or the other way round.
The MOVES buttons sit under PITCH (note), SUB 1 and SUB 2. The SUB outputs are true undertones as V/OCT, not rounded to the scale. In the context menu you can snap them to the scale, per sequencer.
In the Voices view, each row shows the three voices: the voice button (lit = Moves on), the ÷ number for the subs and a level bar. A level of 0 mutes the voice.
Subs Exact / Scale in the bottom bar: Exact keeps the true undertones, Scale snaps them to the scale afterwards. In Rhythmicon the subs are MIDI notes, so Exact rounds them to the nearest semitone. Rhythmicon+ plays them at their exact frequency.
Swing and Density
Swing (50–75 %) delays every second sixteenth: 50 % is straight, 66 % a triplet feel, 75 % a dotted feel. It moves the hits; it never removes them.
Density (0–100 %) leaves out hits. The choice is fixed: at the same place in the pattern it always leaves out the same hits, and turning it up only brings hits back, never different ones. So you can ride it like a fader. The sequencers keep counting through the hits they leave out, a muted step simply does not play. The DENS input adds a CV: 10 V = 100 %. The display shows the left-out hits as rings. Density also thins out the drum notes.
Scale and tuning
Every step snaps to the scale: Off (free pitch), chromatic, major, minor, the church modes, harmonic and melodic minor, major and minor pentatonic, blues, fifths and octaves, above a root. Range sets how far the steps reach: ±1, ±2 or ±5 octaves.
ET · JUST: ET is equal temperament, as on a piano. JUST tunes every note of the scale to a pure ratio of the root (5-limit), so chords and undertones sound without beating. It works when a scale is selected.
The ♭♯ button follows the scale of your Live set (Live's Scale mode), also when you change it. The Scale menu then shows Live.
Jacks
| Jack | Signal |
|---|---|
| CLK | Clock in. Every rising edge is one tick (a sixteenth). Without a cable, TEMPO runs the internal clock. |
| RUN | A trigger toggles start and stop. |
| RESET | Back to tick 0: all rhythms meet again, both sequencers start on step 1. |
| ÷ 1 … ÷ 4 (CV) | Adds to the division: 1 V = 3 steps. |
| DENS | Density CV, 10 V = 100 %, added to the knob. |
| TR 1, TR 2 | Transposition of sequencer 1 and 2, 1 V/oct. |
| TRIG | 10 V whenever a sequencer plays. |
| CLK (out) | The ticks, half a tick long. |
| ÷ 1 … ÷ 4 (out) | Gate of each rhythm, assigned or not. Density applies. |
| V/OCT | Note of the sequencer, 0 V = C4. |
| GATE | Gate of the sequencer, GATE × one tick long. |
| ACC | 10 V on accented steps, as long as the gate. |
| SUB 1, SUB 2 | The two undertones as V/OCT. |
| POLY, P.GATE | Note, SUB 1 and SUB 2 as a three-channel cable, and their gates. Patch it into a polyphonic voice like Shapes and every step plays as a chord. |
Also on the panel: TEMPO 40–240 BPM, SWING, GATE 5–100 % of a tick, RUN and RESET, SCALE, ROOT, RANGE and ET · JUST.
Display and menu
The top line shows the cycle (CYCLE 17 / 420), the tempo or EXT CLOCK, swing, and the scale. On the left, the four rhythm lanes run past a playhead: each dot is a hit, the number on the right says which sequencer it drives (1, 2 or 12), a long line marks the start of the cycle, and the marks below the lanes show where two or more rhythms meet. Hits that Density leaves out are rings. On the right, both sequencers show their four notes; the playing step lights up, a dot marks an accent.
Context menu: Sequencer 1/2: quantize SUB outputs to the scale, Both sequencers on POLY 1 (6 channels), Show values on display and Glass display background.
MIDI out (Rhythmicon)
| Control | Range | What it does |
|---|---|---|
| Play | Notes · Drums · Both | Notes: the sequencers play. Drums: every rhythm plays its own drum note. Both: both at once. |
| Gate | 5–100 % | Note length, as a share of a sixteenth. |
| Drum notes R1 … R4 | 0–127 | The note each rhythm plays in Drums mode, on MIDI channel 10. Factory setting: kick, closed hi-hat, snare, open hi-hat of a Drum Rack (36, 42, 38, 46). |
The note goes out on MIDI channel 1, Sub 1 on channel 2, Sub 2 on channel 3. A polyphonic instrument on the same track plays all three as a chord. To give a voice its own sound, put another instrument on a new MIDI track and set its MIDI From to this track and the channel. The voice level in the Voices view scales the velocity.
Sound (Rhythmicon+)
Rhythmicon+ has two oscillator systems, one per sequencer. Each makes the note and its two undertones at their exact frequency, slightly drifting like analog oscillators. All six voices meet in one mixer, one four-pole ladder filter and one VCA. Every step fires the filter and the amp envelope.
In the Voices view, each system has a Wave menu and a small Shape dial:
| Control | Range | What it does |
|---|---|---|
| Saw | Shape 0–100 % | A second saw, tuned from unison up to the octave. |
| Pulse | Shape 0–100 % | Pulse width. |
| Table | Shape 0–100 % | Position in a formant table: vowel-like colours. |
The panel on the right has two pages:
| Control | Range | What it does |
|---|---|---|
| Cutoff | 20 Hz – 20 kHz | Filter frequency. The value shows while you turn. |
| Reso | 0–100 % | Resonance, up to self-oscillation. |
| EG amt | ±100 % | How far the filter envelope opens (or closes) the filter, up to ±6 octaves. |
| VCF · Attack, Decay | 0.5 ms – 5 s, 5 ms – 10 s | Filter envelope, with analog curves. |
| VCA · Attack, Decay | 0.5 ms – 5 s, 5 ms – 10 s | Amp envelope. |
| Drive | 0–100 % | Drives the mixer into the filter: warmer and louder towards the right. |
| FM 2 → 1 | 0–100 % | Oscillator 2 modulates oscillator 1, the subs of system 1 follow. |
| Volume | −70 … +6 dB | Output level. |
Destroy page, everything before the filter, so the filter can tame it again:
| Control | Range | What it does |
|---|---|---|
| Ring | 0–100 % | Ring modulation of oscillator 1 by oscillator 2. |
| Fold | 0–100 % | Wavefolder: more harmonics, metallic at the top. |
| Fold EG | 0–100 % | The filter envelope drives the folder: every step shouts and settles. |
| Rate | 200 Hz – 48 kHz | Sample-rate reduction, like an old sampler. 48 kHz = off. |
| Bits | 1–16 | Bit reduction. 16 = off. |
Transport and Link
Rhythmicon runs with Live's transport and follows the song position, so its hits always sit in the same place in the bar. When you start, loop or jump, both sequencers begin again on step 1. The tempo comes from your set.
Link (bottom right) connects Rhythmicon with other Thoow devices on other tracks, such as our coming bass device. Leave it on A for now.
First patches
- Chord on one cable: POLY 1 into V/OCT and P.GATE 1 into TRIG of Shapes. Every step plays the note with both undertones.
- Three oscillators, like the original: V/OCT, SUB 1 and SUB 2 of a sequencer into three oscillators, through one filter and VCA, GATE into the envelope.
- Drums: the four ÷ outputs into four drum voices: four-against-three-against-five-against-seven.
- Breathing groove: a slow LFO into DENS: the pattern thins out and fills up again, always with the same hits.
- Drone and melody: MOVES off for the note, on for both subs: the subs walk, the note holds.
- Rhythmicon with Drift or Wavetable: drop Rhythmicon in front of a polyphonic synth with a soft pad sound. Each step plays a three-note chord.
- Drum Rack: Rhythmicon in front of a Drum Rack, Play = Drums. Change the ÷ numbers and listen to them meet.
- Rhythmicon+ dub stab: Cutoff low, EG amt high, short VCF and VCA decay, then a delay and reverb after it.
- Breathing groove: map Density to a macro, or let Thoow Motion move it slowly.
- Drone and melody: in the Voices view, switch off the note and keep both subs moving, or the other way round.
Changelog
2.1.0 · 19 October 2026
- First release: four rhythms, two sequencers, undertone and POLY outputs, 16 scales and just intonation.
- DENSITY with CV input, MOVES per voice, SUB quantizing per sequencer, a chord as the factory setting.
VCV Rack 2 only loads plugins whose version starts with its own major number, so the version starts with 2.
Rhythmicon and Rhythmicon+ 1.0.0 · 19 October 2026
- First release for Ableton Live 12 with Max for Live.
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Credits
After the Rhythmicon by Henry Cowell and Léon Theremin (1931). Inspired by the Moog Subharmonicon; not affiliated with Moog Music. Design, code, panel and display by thoow, Hamburg.
Ableton and Live are trademarks of Ableton AG. Max is a trademark of Cycling '74.
Questions or feedback: service@thoow.com