FERAL — nine noisy, unpredictable synthesis models for the Model:Cycles

FERAL is one added machine for the Elektron Model:Cycles, OS 1.13: nine noisy, unpredictable synthesis models on one machine, light on the processor. COLOR and SWEEP are the model's two macros; CONTOUR is the tone envelope (or a third control on BNJ and RNG); PUNCH is FREE.

This repository is the machine's source package, published so that other projects can port it. It is not a firmware and contains none.

Hear it: FERAL on YouTube
Flasher: 100demons.github.io/cycles-engines/flasher — tick FERAL and bring your own official model-cycles_OS1.13.syx.

The models

SHAPE picks the model. The names are shown on the machine's screen.

SHAPE	Model	What it is
0	NYB	Nyblcore: bytebeat formulas over an 8 kHz counter
1	GND	Gendy: per-period waveform from random-walk points
2	BNJ	Benjolin: two triangles plus an 8-bit rungler clocked by OSC2
3	RYT	Rhythmicon: ten partials as 2-pole ping resonators
4	FRS	Fourses: four points reflecting between neighbors, averaged
5	RNG	Rungler: 8-bit register quantized to fifths/octaves
6	PLS	Pulsar: windowed sine pulses at COLOR × pitch
7	SCN	Scanned synthesis: 32-mass ring scanned at note pitch
8	KOS	Chaotic map: x → r·x(1−x), 16 iterations per period

The knobs

Knob	What it does
PITCH / FINE	the note, as on every machine
COLOR	the model's first macro; the value window names the real control for that model
SHAPE	the model (the table above)
SWEEP	the model's second macro
CONTOUR	the tone envelope; a third control on BNJ and RNG
DECAY	the stock amp envelope
GATE	on, with extended note lengths, is recommended for all synthesis types
PUNCH	the FREE switch: off, each trig restarts the engine; on, it keeps running between trigs, so patterns drift. On BNJ it locks the random loop into a repeating cycle

Status

Package	cycles-mod/0.1, the model27/cycles-engines package format
Slot in the flasher	7 (the OS numbers it machine 6)
Committed object	feral.o; core/build_engine.py feral --check passes
Emulated	the source tree's nine-model voice-loop proof, 2026-10-22
Tested on a real Model:Cycles	yes — 2026-10-22, standalone; the composed package build is new
Weight	the worst model is 4,801 instructions per 32-sample block, against 5,290 for TONE
License	MIT

FERAL is the only one of the flasher engines that has been played on hardware. The hardware test covers the standalone build; the package's own composed build has not been separately tested.

Package layout

tools/machines/feral/
  manifest.json    the package: build recipe, symbols, claims, tests, compatibility
  card.json        the flasher card: label, description, status, video
  tiny2.c          the voice-loop bridge
  tiny2_dsp.h      the model dispatcher and shared DSP
  tiny2_eng_a.h … tiny2_eng_e.h   the nine models
  tiny2_tables.h   the generated tables
  feral_ui.S       the custom SHAPE names through the registrar runtime
  feral_icons.h    the machine-page splash
  feral.o          the committed relocatable object
  LICENSE          MIT

There is no firmware here: the package is applied to the user's own official OS file by a host such as cycles-engines.

Build and check the object

The package builds with the cycles-engines toolchain. Copy tools/machines/feral/ into a cycles-engines checkout as engines/feral/, then:

export M68K_CROSS=/path/to/bin/m68k-elf-        # or have m68k-elf-gcc on PATH
python3 core/build_engine.py feral --check

--check rebuilds feral.o from the sources and the manifest's recipe and compares it with the committed object. The composer and the flasher never need the toolchain: they place the committed object.

Install

Easiest: tick FERAL in the flasher and bring your own official OS 1.13 file. Or download feral-9.0.zip from this repository's Releases and add the folder to your own build.

Credits

• Engine, tables and design: 100demons and Claude, MIT.
• See THIRD-PARTY-NOTICES.md.

Changelog

See CHANGELOG.md.