README from GitHub, GPL-3.0

CHONK

A physically modeled electric bass for Schwung on the Ableton Move.

Ported from OneTrick CHONK by Punk Labs LLC — the bass model is entirely theirs. It is free as in rights, not as in beer: if you play this, buy a copy.

One modelled string: bridge and nut terminations, a pickup tapped part-way along it, a finger pluck and a noise transient at the strike. A hard note rings differently from a soft one because the string is being hit harder — not because a different sample was chosen.

Manual

Playing

Range C3–G6 (MIDI 48–91). Notes outside it are ignored rather than folded in: below, the waveguide runs out of delay line; above, the model goes unstable. Upstream clamps the same window.

Monophonic by design. A new note takes the string over; releasing it hands the string back to the note below without re-plucking. That handover is how one string works — it is not the Legato switch, which is off by default.

Play hard (velocity 108 and up) and it slaps on its own — upstream's articulationSlapAuto.

The pads

The octave below the playing range is articulation, and moves with the module's octave shift so the row stays reachable.

Pad		Pad
C2	Mute	E2	Pick
C#2	Slide down	F2	Slap
D2	Finger	F#2	Legato
D#2	Slide up	G2	Ring
		G#2	Alt Pick

A held pad always wins, and never moves the parameter. Style pads select that style while held, then hand back to the Style setting. Mute and Legato pads invert their switch — with Mute latched on, hold the pad to play one open note. Slide pads bend for as long as they are held, scaled by velocity.

Knobs and pages

The front page is the string, and the sub-pages split by hand — what the striking hand is doing, and what happens between notes.

root  ·  the string                        + preset browser
  1 Pickup   2 Bright   3 Tone             timbre
  4 Thump                                  attack body
  5 Sustain  6 Ring                        how long it holds, how it lets go
  7 Sat      8 Volume                      output

  Attack     Style · Strike · Mute · Alt Pick · Pick Depth
  Fretting   Legato · Glide · Glide Time · Frets · Retrigger
  Output     Volume · Pan · Sat · EQ 100 · 250 · 500 · 1.5k · 3k
  MIDI       Fine Tune · Bend Range · AT Range · Vel Sens

Style and Strike Hardness share a page because they are one control — a style does nothing but replace Strike with a fixed value. Split across pages, as they were, the knob reads as broken. Saturation and Volume are on the root knob row but live on Output; a level's knobs need not be in its own params, so the row is what you play while the menu stays the string and four doors.

Pickup Pos moves the pickup along the string — low is fat and neck-ish, high is nasal and bridge-ish. Tone is the passive tone control, a 1-pole lowpass from 300 to 2500 Hz. Volume runs −60…+6 dB, a narrowed slice of upstream's −100…+6 (the bottom 40 dB are all silence).

Attack and Fretting

Style — Off / Finger / Pick / Slap. One choice, not four switches: in the model a style does nothing but replace the Strike Hardness knob with a set value — Finger 0, Pick 50, Slap 100, Off the knob. So Off with Strike Hardness at 100 is Slap, bit for bit.

Mute damps the string fast and dull and gives the attack its own extra thump. While it is on the Thump knob is out of circuit.

Legato is a sound, not a note-handling mode: it glides the pitch over 35 ms stepping through frets, and takes the click and the finger out of the output. The note-to-note handover happens with Legato off as well.

Glide, Glide Time and Frets are the first two of those broken out. Glide slides between held notes while keeping the click, over Glide Time — 0–500 ms, higher is slower, defaulting to upstream's fixed 35 ms; Legato still implies glide, so Legato alone sounds exactly as it always has. Frets sets the path a glide takes — on, it walks up the frets; off, it slides smoothly past them — and defaults on, which is how upstream always played. All three only matter when one note is held into the next; with Glide and Legato both off, Glide Time does nothing at all, because the DSP multiplies it by glideTerm.

Alt Pick plays the line down, up, down, up instead of every note being a downstroke. Three things separate the two strokes: the pick pushes the string the other way (the part you hear against a string that is still ringing), the upstroke carries about 18% less energy, and its click is thinner, brighter and shorter. A phrase starts on a downstroke, and the count restarts after a rest of ~1 s — time with nothing held. The string may still be ringing; hands off the pads is the rest. A held note is never a rest at any length, and neither is a sustain pedal holding notes. Not on release (picking is separate notes, so that would make every note a downstroke), and not on a gap between attacks either: measured that way, a quarter note at 120 bpm is a 500 ms gap, so anything slower than eighths came out all downstrokes and a held note reset itself mid-ring. Pad G#2.

Pick Depth scales that separation: 100% is the voicing tuned by ear, 0% leaves only the direction flip, 200% doubles it. It deliberately does not touch the direction — that part is physically true and it is binary, and scaling it would put the upstroke's excitation at zero around 50% and drop every other note. What scales is the three magnitudes, which were the judgement calls.

Retrigger decides what an overlapping note does. Off (the original): a second note at the same velocity re-pitches the ringing string without re-plucking; at a different velocity it plucks. On: every note-on plucks.

Ring sets how far the release damps the string — 0 is the original's hard stop, 100 leaves it undamped to decay on its own. The G2 pad rings the string out while held, whatever the knob says.

MIDI

Pitch bend by Bend Range (0–12 st). Aftertouch bends by AT Range (−2…+2 st; negative bends down). Fine Tune detunes ±100 cents. Vel Sens sets how far velocity moves the sound — at 0 every note plays as velocity 80.

CC 1 mod wheel opens the sustain all the way up · CC 64 sustain holds notes · CC 68 legato · CC 120/123 all notes off.

Presets

Nine, from Punk Labs: J-Bass, Defender, Demonster, Disco, Flatworm, Gargantuan, Justice, New Strings, Sitcom. They set the String, EQ, Mix and MIDI pages, and reset the switches this port added — Glide, Glide Time, Frets, Ring, Alt Pick, Retrigger — because those are part of the sound. Upstream's own articulation (Style, Mute, Legato) is left alone, because that is how you are playing rather than what the patch is.

On-device help covers all of the above (Shift+Vol+Menu → Help → Modules).

Behaviours that read as broken knobs

Both are upstream's design, and both were measured rather than assumed:

Strike Hardness is subtle, and often bypassed entirely. bass.dsp:122 interpolates away from the knob as articulationStyleAmount rises, so any engaged Style takes it out of circuit — and since articulationSlapAuto ramps in from velocity 0.85, a hard-played note does too. A 0 → 100 sweep at velocity 127 changes the output by nothing at all (rms 0.08413 either way); at velocity 100 it moves peak 0.41 → 0.34.

Thump is disabled by Mute and by Legato. extraThump is pinned to 1.5 when Mute is on, and the whole term is multiplied by (1 - articulationLegato). With neither engaged the knob is strong — attack rms 0.048 → 0.205 across its range.

./scripts/render.sh renders both as A/B pairs, alongside the styles, Ring and Retrigger.

How it was ported

The synth is Punk Labs' Faust code. src/dsp/faust/bass.dsp (the string) and output.dsp (EQ → saturation → panner) sit beside their onetrick.lib and params.lib. scripts/gen_dsp.sh compiles them to C++ with upstream's own build line, -lang cpp in place of -lang rust, into src/dsp/generated/ — machine output, never hand-edited.

What this repo replaces is upstream's nih-plug/egui host. src/dsp/chonk_plugin.cpp is the plugin_api_v2 wrapper: the voice logic (transcribed from OneTrickMonoVoice, edge cases included), the MIDI surface, and the parameter surface Schwung reads.

Three changes were made to the DSP, all marked SCHWUNG PORT ADDITION.

The first is the Ring release control. Upstream damps the released string to a fixed bounceEfficiencyMuted = 0.5 with no control over it; Ring interpolates the release efficiency between that and the open value, and does it geometrically in the decay rate — which is linear in the log of the ring time, so every step of the knob multiplies the ring by the same ratio.

That mapping took two goes, and the first one is worth recording. Interpolating the log of the two efficiencies is linear in the rate, and ring time is 1/rate, so the time came out a hyperbola: 7× the minimum at 90% of the knob, then a 47× jump in the last tenth. Both endpoints were exactly right either way, so every test stayed green — it just played dead, which is the only way an error in a mapping ever shows up. Measured, to -40 dB after release:

ring	0	10	25	50	75	90	100
before	0.12 s	0.15	0.15	0.21	0.39	0.85	5.80
after	0.12 s	0.18	0.33	1.04	3.36	5.80	5.80

At 0 it returns upstream's release to the sample; at 100 the release stops damping entirely, so a released note decays exactly as a held one does. The top of the knob flattens because the string's own Sustain is the ceiling — Ring decides how much of it you keep, it cannot add more.

The second is alternate picking: a Pick_Up entry the wrapper writes one stroke at a time, driving the excitation's sign, its energy and the transient filter's corners. Deliberately unsmoothed — it has to be right at the trigger edge, and a ramp between strokes would make every pluck half of each.

The third splits Glide and Frets out of Legato. Upstream welded three behaviours together: stringSlide glided only under articulationLegato, and quantizeFrets fretted only under Legato or an active slide pad. They are now their own controls, with glideTerm = max(legato, glide), articulationFrets defaulting on, and the hard-coded 35 ms replaced by a glideTime slider that defaults to 35 — so every combination that existed before behaves as it did.

Retrigger needed no DSP change but is not a flag either: Faust fires the pluck on a rising edge of Trigger, which a block-rate host cannot manufacture by writing the zone twice between blocks. The wrapper drops the zone to 0 and lets render_block split one frame off the front and raise it after. The pluck lands a sample late; no audio is lost, unlike upstream's burn_sample, which discards the frame it advances.

The original source drop is kept under original source/ for provenance.

Building

./scripts/build.sh      # cross-compile for Move via Docker -> dist/chonk-module.tar.gz
./scripts/install.sh    # deploy to ableton@move.local (MOVE_HOST to override)
./scripts/test.sh       # host-side tests + help lint, no device needed
./scripts/render.sh     # audition/A-B WAV -> build/chonk_demo.wav
./scripts/gen_dsp.sh    # regenerate the C++ from the .dsp sources (brew install faust)

Faust is needed only to regenerate the DSP; the build container carries a cross compiler and nothing else.

Two files are generated from the wrapper and are regenerated by build.sh: src/module.json's ui_hierarchy, and src/dsp/factory_bank.h — which is indexed by PARAMS[] position, so adding a parameter without regenerating loads every preset value past it one slot out, silently.

Credits and license

Move port by legsmechanical.

Released under the GNU General Public License v3.0 or later, inherited from OneTrick CHONK. LICENSE is upstream's copy; original source/OneTrickCHONK-Source-v1.0.0/NOTICES.txt carries the full third-party acknowledgments — Faust's standard libraries (Julius O. Smith III's filter and waveguide work among them), nih-plug, and the rest.

This program is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your option)
any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.