Mook D — Model D-style synth module for Ableton Move (Schwung)

A monophonic Minimoog Model D-style sound_generator module for the Schwung framework. Three oscillators into a 4-pole transistor ladder low-pass filter, with independent filter and loudness contour envelopes, glide, and osc-3/noise modulation.

Written natively to the Schwung Plugin ABI (move_plugin_init_v2, 44100 Hz / 128-frame blocks, stereo interleaved int16). No vendor source reused.

Signal path

Osc1 ┐
Osc2 ┼─ Mixer ─→ Ladder LPF ─→ VCA ─→ out
Osc3 ┘           (cutoff/emphasis/    (loudness
Noise┘            contour env)         env)

Editing the Model D surface

Mook D is not preset-only. The root page deliberately reserves its eight immediately reachable controls for filter and contour performance; open the named sections below it to edit the rest of the instrument:

Model D area	Mook D section	Editable controls
Oscillator bank	Oscillator 1 / 2 / 3	Range, waveform, Osc 2/3 tune, Osc 3 keyboard control
Mixer	Mixer	Each oscillator level, noise level/color, volume
Filter	Ladder Filter	Cutoff, emphasis, contour, filter ADS, key tracking
Loudness contour	Loudness Contour	Attack, decay, sustain, Model D decay switch
Controllers	Controllers	Glide, master tune, osc-3/noise modulation mix and pitch/filter routes

The separate LFO, hard sync and filter FM are Mook D additions rather than replacements for those classic controls.

DSP notes

• Oscillators: PolyBLEP band-limited saw/pulse/square + naive triangle. Ranges LO/32'/16'/8'/4'/2' map to octave multipliers; osc 3 can free-run (o3_kbd = Off) to act as a modulation oscillator. Fundamentals above the useful audio band fade before Nyquist instead of folding into a fixed high-pitched tone.
• Filter: Huovilainen-style nonlinear 4-pole ladder, 2× oversampled, with per-stage tanh saturation. Cutoff combinations use a soft upper ceiling; the ceiling lowers as emphasis rises to keep resonant peaks musical.
• Envelopes: exponential ADSR. The Model D Decay switch (decay_sw) makes release track the decay time; Off gives a short release.
• Voice: mono, last-note priority with an 8-deep held-note stack, glide.
• Mod: mod_mix crossfades osc 3 ↔ noise; route to pitch and/or cutoff.
• LFO: dedicated modulation oscillator — Rate (0.05–40 Hz, log), Shape (Tri / Ramp Up / Square / Ramp Dn / S&H), independent depths to pitch (vibrato) and filter cutoff. Tempo sync (lfo_sync) locks the rate to host BPM via get_bpm() at a musical division (lfo_div, 4 bars…1/32 incl. triplets); free-runs otherwise. Separate from the osc-3/noise mod bus.
• Hard sync: osc_sync makes Osc 1 the master and resets Osc 2 (and optionally Osc 3) phase on each master cycle — the classic sync-lead tear.
• Filter FM: filt_fm routes Osc 3 into the ladder cutoff at audio rate for growl/formant tones (inharmonic when Osc 3 free-runs, o3_kbd = Off). Filter FM, routed modulation and filter LFO depth are independently bounded.
• Control safety: Continuous filter, pitch, mixer and volume controls are smoothed per sample. The plugin validates every string parameter at the ABI boundary and clamps non-finite or out-of-range input.
• Presets: 32 native patches (preset param) authored for this module's ranges, spanning bass/lead/pad-drone/bell/FX character. Nothing copied from other projects — their values are calibrated to different DSP and wouldn't map — though the category vocabulary and naming take inspiration from open-source Minimoog emulators (e.g. stevebarakat/Minimoog's Bass/Lead/ Pad/Experimental preset bank).

Build (ARM64, requires Docker)

./scripts/build.sh
# → dist/mook-d/{dsp.so,module.json,help.json}
# → dist/mook-d-module.tar.gz

The Dockerfile pins gcc-aarch64-linux-gnu; flags mirror the reference modules (-O2 -shared -fPIC -ffast-math -lm) and avoid shm_open so the GLIBC requirement stays at the Move's runtime level.

Run the adversarial native DSP checks with ./scripts/test-dsp.sh. They use AddressSanitizer/UndefinedBehaviorSanitizer and fuzz combined control values, MIDI extremes and truncated packets.

Install on the Move

Copy the built folder to the Move's modules directory (via schwung-manager or scp), so it lands at .../modules/mook-d/ containing dsp.so + module.json, then load Mook D from the sound-generator list. It's chainable, so it also works as a Signal Chain generator.

Starting patch — classic fat bass/lead

Section	Setting
Osc 1	8′, Saw
Osc 2	8′, Saw, Tune −0.07 st
Osc 3	16′, Saw, Tune +0.05 st, Kbd On
Mixer	O1 0.8 · O2 0.7 · O3 0.5 · Noise 0
Filter	Cutoff 0.38 · Emphasis 0.25 · Contour 0.45
Filter env	A 0.005 · D 0.35 · S 0.30
Loudness env	A 0.005 · D 0.5 · S 0.8
Controllers	Glide 0 · Master Tune 0 · Decay Sw On

For the pitch-wobble variant: Osc 3 → LO range, o3_kbd Off, mod_mix 0, mod_osc On.

Presets

Original 16: Init · Fat Bass · Sub Bass · Rubber Bass · Classic Lead · Brass · Funk Lead · Wobble Bass · Vibrato Lead · Sci-Fi Sweep · Bright Pluck · Detuned Stab · Whistle · Noise Sweep · Sync Lead · FM Growl.

Expansion 16: Taurus Sub · Slap Bass · Dub Bass · Growl Bass · Warm Pad · Glass Pad · Cathedral Drone · Prog Solo · Screamer Lead · Watery Lead · Simple Lead · Crystal Bells · Wind Chimes · Submarine Sonar · Alien Signal · Cosmic Drone.

Wobble/Sci-Fi/Vibrato/Whistle/Noise/Wind Chimes/Submarine Sonar/Cosmic Drone use the LFO (Wobble and Cosmic Drone are tempo-synced); Sync Lead and Alien Signal use hard sync; FM Growl, Crystal Bells, Growl Bass and Alien Signal use filter FM.

Contributing upstream

See PR_CHECKLIST.md. Schwung requires disclosing AI tooling in the PR (this was built with Claude and OpenAI Codex) and does not accept Grok work.

Third-party

The Schwung Plugin API header (src/dsp/host/plugin_api_v1.h) is MIT © Charles Vestal — see THIRD_PARTY.md. Everything else is original.

License

MIT.