A chaos-driven FM synthesizer device for Ableton Live 12 (Max for Live, instrument). Four classic strange attractors (Lorenz, Rössler, Aizawa, Thomas) integrate at 200 Hz inside a JS engine and modulate a 2-operator FM voice in real time — chaos as a never-repeating, bounded modulation source. The attractor's trajectory is rendered live as a triple-trace scrolling oscilloscope across the bottom of the device.
- Four strange attractors — Lorenz (classic butterfly), Rössler (single-loop), Aizawa (spiraling sphere), Thomas (gentle cyclic drift). Each gives a distinct chaos signature.
- Chaos modulates ratio, FM index, and amplitude — the attractor's three axes drive different parameters of the FM voice in parallel; depth scales how strongly chaos overrides the static dial values.
- 2-operator FM synthesis — phasor~/cos~ pair with phase-mod, carrier ratio + index controls, drive (tanh saturation), and an ADSR envelope.
- Velocity-aware — per-note level scales with MIDI velocity; envelope normalised so high velocity doesn't overshoot.
- Glide / portamento for legato lines.
- Full bottom-strip visualizer — triple-trace oscilloscope (one trace per chaos axis), per-mode color palette, motion blur, glow, auto-scaling and DC-blocking so every attractor shows up centered regardless of its natural offset.
- Note-gated animation — the visualizer fades when no notes are held; chaos engine can also be toggled OFF entirely (greying out the chaos-only controls so the inert state is obvious).
- Self-contained
.amxd—attractor_viz.jsis embedded inside the frozen Live device. Drag one file and it works. - All parameters automatable, mappable, and annotated for Live's hover-info panel.
- Drag
Attractor.amxdfrom the repo into a MIDI track in Ableton Live 12 (or copy to your User Library). - Play any note — chaos engine is ON by default; the FM voice and visualizer fire up immediately.
- (Optional) Map any dial to a Live macro / MIDI controller via right-click → Map.
| Name | Type | Range | Description |
|---|---|---|---|
| Chaos | toggle | off / on | Master switch for the chaos engine |
| Type | menu | Lorenz / Rössler / Aizawa / Thomas | Strange-attractor algorithm |
| σ | dial | 1–30 | Lorenz σ (Prandtl number) — wilder swirl when higher |
| ρ | dial | 1–50 | Lorenz ρ (Rayleigh number) — below ~24 the system settles |
| β | dial | 0.1–10 | Lorenz β — vertical damping; classic value 8/3 ≈ 2.667 |
| Speed | dial | 0.0001–0.02 (exp) | Integration step size |
| Ratio | dial | 0.25–8 (exp) | FM modulator-to-carrier frequency ratio |
| Index | dial | 0–10 | FM modulation index (0 = pure sine, higher = brighter) |
| Attack | dial | 1–2000 ms (exp) | Note attack time |
| Release | dial | 5–4000 ms (exp) | Note release time |
| Depth | dial | 0–1 | Strength of chaos modulation across ratio / index / amp |
| Drive | dial | 0–1 | Soft saturation (tanh waveshaper) on the carrier |
| Glide | dial | 0–500 ms (exp) | Portamento between notes |
| Volume | dial | -60 to +6 dB | Output level (per-note level also scales with MIDI velocity) |
Hover over any control in Live to see the description in the bottom info panel.
DSP voice: [midiparse] → [stripnote]/[unpack] (parallel paths so velocity reaches [adsr~] for both note-on and note-off; stripnote only fires on note-on so mtof doesn't glitch under legato) → [mtof] → [pack freq glide_ms] → [line~]. Velocity is divided by 127 before [adsr~] so the envelope tops out at ≤1.0 (avoids volume overshoot). Carrier [phasor~] → +~ PM offset → [cos~] → [*~ drive_scale] → [tanh~] → *~ envelope → *~ (1 + z·depth·0.3) (chaos amp mod) → *~ 0.5 (trim) → *~ dbtoa(volume) → [tanh~] (final brick-wall safety limiter) → [plugout~ 1 2]. The volume dial is implemented manually via dbtoa → pak 0.0 20. → line~ → *~ rather than live.gain~ so the dB curve and parameter range can be tuned independently of Live's stock gain widget.
Chaos engine: attractor_viz.js runs both the integrator (Lorenz/Rössler/Aizawa/Thomas, ~600 substeps/s) and the visualizer in a single [jsui]. The integrator writes back to outlets 0/1/2 (x/y/z) which feed line~-smoothed signals into the FM voice. The metro that drives the JS is gated by [snapshot~] of the envelope AND the chaos toggle — chaos integrates only while a note is held, which is what stops the visualizer from animating with no input. A separate always-on slow metro 50 → "fade" keeps the fade-out animation running after notes release.
build_attractor.py is the patch generator — it composes the .maxpat JSON programmatically. pack_amxd.py then packs the patch + attractor_viz.js into a self-contained frozen .amxd binary container (ampf → meta → ptch → mx@c chunks with an embedded directory of files). No external template file is needed.
- Ableton Live 12 required — uses Live 12 device-height conventions (169 px) and modern parameter init layout.
- Max for Live 8.5+.
- Built and tested on macOS. Windows untested but should work — only the build script touches macOS-specific code paths.
build_attractor.py and pack_amxd.py (Python 3.11+) generate the .maxpat and the frozen .amxd respectively. Edit the source and re-run:
python3.11 build_attractor.py # regenerates Attractor.maxpat
python3.11 pack_amxd.py # packs into Attractor.amxdThe .amxd binary container is the frozen format Max produces from "Freeze Device":
'ampf' [LE u32 = 4] "iiii" ← device-type tag (instrument)
'meta' [LE u32 = 4] uint32_LE(7) ← format version (frozen)
'ptch' [LE u32 = N]
'mx@c' [BE u32 = 16] ← data offset (constant)
[BE u64 = footer_offset] ← absolute from 'mx@c' byte 0
[patcher JSON] ← Attractor.maxpat
[attractor_viz.js bytes]
'dlst' [BE u32 = N] ← embedded-files directory
'dire' entries (type, fnam, sz32, of32, vers, flag, mdat)
The script generates this structure directly — no external .amxd template needed. The frozen format matches what Max's own Freeze Device produces, so the output drops straight into the User Library and works without any loose .js files alongside.
Adrian Kwiatkowski — electronic music producer.
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MIT — see LICENSE. You can edit, modify, redistribute, and use ATTRACTOR in commercial productions; please retain the copyright notice in derivative works.