rytm1_mods
Unofficial community firmware mods for the Analog Rytm MK1 (OS 1.73): SMP CUT per-track low/high cut, euclid accents, velocity humanise
About
Highlights
- SMP CUT build: press FILTER twice for a low cut and a high cut per track on the sample layer
- RANDOM build: press LFO twice for two random modifiers per sound
- Both builds: Euclidean accents and velocity humanise (TRIG page, FUNC + VEL)
What you need
Your own stock Analog Rytm MKI OS 1.73, Python 3.11+, git, make, a C compiler and m68k binutils. Keep a physical DIN MIDI interface for recovery.
Good to know
The two builds cannot be combined because they share one stored value. The changes are marked as built, not as verified on hardware. Recovery: FUNC at power-on, TRIG 4, then the stock 1.73 file over DIN MIDI with Transfer's legacy mode.
README
rytm1_mods
Firmware modifications for the Analog Rytm MK1, OS 1.73 - a port of the MKII
project rytm-mods (kept unchanged next to this folder as rytm-mods_MKII_peer),
with the same conventions: every build starts from the pinned stock image and
rebuilds from source; the patch sources, the symbol map and the allocation registry
are the project, the .syx is an artifact.
Unofficial. Not affiliated with or endorsed by the manufacturer. Flashing modified
firmware is at your own risk; keep the stock .syx for recovery (docs/FLASHING.md).
What it looks like
Two builds, one new page each (mockups at the MK1 screen's 122 x 32 pixels; the stock page code draws the real thing).
SMP CUT build - press FILTER twice: a low cut and a high cut per track, on the sample layer.
RANDOM build - press LFO twice: two random modifiers per sound. DS picks the destination, DP the depth; every note adds a random -N..+N to it.
Both builds also carry euclid accents (OP values OR* XOR* AND* SUB*) and velocity humanise (TRIG page, FUNC + VEL). Details in docs/MANUAL.md.
Layout
| path | what |
|---|---|
stock/ |
the stock MK1 1.73 .syx and its checksum. Never written to. |
re/symbols.toml |
the MK1 symbol map: every address, the MKII address it ports, and the evidence |
registry/allocations.toml |
cave pools and every claim on them, detour and patch sites (MK1 addresses) |
mods/NNNN-slug/ |
one modification: manifest, stub source, design notes |
tools/ |
build, layout check, verify, symbol generation; xmatch.py (MKII -> MK1 address matcher); mkelemod.py / elemod_check.py (the elekloader export and its proof); gen_cut_tables.py (0008's filter tables); eft-ele2-align4.patch |
vendor/ |
elektron-firmware-tool, fetched and patched by make setup |
docs/ |
MANUAL (what the mods do), FLASHING, HAZARDS (read it) |
PORTING.md |
what is ported, how, what differs from MKII, what is left, the loader question |
build/ |
artifacts |
Build
Prerequisites: Python 3.11+, git, make, a C compiler, and m68k binutils
(brew install m68k-elf-binutils on macOS, apt install binutils-m68k-linux-gnu
on Debian/Ubuntu - either prefix is found automatically).
make setup # clone the container tool at its pinned commit, apply the MK1 patch, build it
make verify # the SMP CUT build: 0000 + 0002 + 0003 + 0008, and assert the result
make random # the RANDOM build: 0000 + 0002 + 0003 + 0004, and assert the result
make control # the pipeline test: no mods, stock code repacked
make verify produces build/AR1_OS1.73_0000_0002_0003_0008.syx, make random
build/AR1_OS1.73_0000_0002_0003_0004.syx. There are two builds because 0004 and
0008 keep their settings in the same free word of the sound - the only one the stock
OS saves, loads, copies and undoes by itself - so they can never share an image.
A subset, for bisecting on hardware:
python3 tools/build.py --mods 0000-shared 0002-euclid-accents
Choosing mods in elekloader
The same workflow as the Digitakt mods: make elemod writes one .elemod per mod
to build/elemod/, and elekloader (with its Analog Rytm mk1 profile) lets you tick
the ones you want, checks them against each other, builds the .syx on your stock
file and verifies it. The mods are patch sets at fixed addresses (format 1, no
boot-time loader), so a combination is exactly what tools/build.py --mods ...
would build - make elemod-check ELEKLOADER=path/to/elekloader proves it for every
combination, and that elekloader refuses 0004 + 0008 and any mod without what it
needs.
| mod | needs | cannot go with |
|---|---|---|
| 0000 Shared runtime | - | - |
| 0002 Euclid accents | - | - |
| 0003 Velocity humanise | 0000, 0002 | - |
| 0004 LFO RND | 0000 | 0008 |
| 0008 SMP CUT | 0000 | 0004 |
elekloader packs the MAIN OS with its own packer, so its .syx is ~15% larger than
the one make writes (the MAIN OS inside is identical).
The MK1 container
One section, not five:
| id | name | size | load base | we touch it |
|---|---|---|---|---|
| 3 | MAIN OS | 2,824,228 | 0x40000400 | yes - but never 0x4028c708..0x402a1b24, the embedded bootstrap |
Mods
| id | title | MK1 status |
|---|---|---|
| 0000 | The shared runtime other mods call into | built |
| 0002 | Euclidean generator places accents instead of trigs | built |
| 0003 | Per-track random velocity offset | built |
| 0004 | LFO RND: two per-sound random modifiers on a second LFO page | built (RANDOM build; excludes 0008) |
| 0006 | Compressor gain-reduction preview | not ported (disabled, not wanted) |
| 0008 | SMP CUT: low cut / high cut per track on a second FILTER page (new, MK1 only) | built (default build; excludes 0004) |
Status ladder: re-only -> built -> hardware-verified, plus retracted. Only
hardware-verified counts, and MKII results do not transfer automatically.
Pictures in the README load from GitHub.
- Language
- Assembly
- Stars
- 1
- Forks
- 1
- Created
- 09-28-2026
- Last commit
- 6 days ago