elektron-firmware-tool

An unofficial C tool to inspect and modify Elektron instrument OS files (.syx). Not affiliated with or endorsed by Elektron.

What it does

An OS .syx is a SysEx transport wrapping a container of compressed sections. The tool can:

• inspect: report the layers and check the stored checksums
• decompress: write each section out as a raw file
• modify: replace a section (or set the version string) and recompute the checksums so the rebuilt .syx stays consistent

Container formats: ELE3, ELE2, ELEK, AD, and the older pre-ELE (Machinedrum / Monomachine).

Build

make

Usage

elektron-firmware-tool -i <in.syx>                             summary + checksum verdict
elektron-firmware-tool -i <in.syx> -v                          full report, every layer
elektron-firmware-tool -i <in.syx> [-d N]... -o <outdir>       decompress sections
elektron-firmware-tool -i <in.syx> [-c N <file>]... [-V VER] -o <out.syx>   rebuild

Without -o, the default output is a one-glance summary listing the section ids you can pass to -d and -c; -v adds the full per-layer report. Each -c takes exactly one id and one file, and may be repeated.

-h lists all options.

Compression level

-l N trades rebuild time against output size by bounding how many match candidates the packer examines per position. 0 is fastest, 3 (the default) smallest; the range spans roughly 16x in time for about 4% in size. Every level produces a valid stream.

-l only affects -c. Inspecting and decompressing are unaffected.

Emitting the container

--emit-container F writes the bin layer — the container inside the SysEx transport — to F, in addition to whatever the command already does. With -i it is the container as parsed from the input; with -c/-V/-r it is the rebuilt one, taken at the point the transport encoder receives it, so for ELE3 it already has the version and the HMAC trailer applied. The two agree byte-for-byte on an unmodified rebuild.

Byte-exact repacking

-r rebuilds a file without changing anything. Sections are copied verbatim rather than recompressed, so the whole pipeline — transport decode, container parse, container assembly, transport encode — has to be lossless for the output to match, which makes it a useful self-check:

elektron-firmware-tool -i OS.syx -r -o repacked.syx && cmp OS.syx repacked.syx

This reproduces 22 of the 23 images tested exactly. The one exception has a stray 0x0A after its final F7, outside the SysEx stream altogether, and is byte-identical up to that.

Note that a file rebuilt with -c is not byte-identical even if the replacement matches what was there, because this packer makes different (better) choices than the one Elektron used. What -c preserves is the decompressed content of every section; -r is what preserves the bytes.

Structure

Split by protocol layer, following the path a file takes: transport → container → section → codec. Each layer's format constants live in its own header.

Notes

Intended for inspection, interoperability, research, preservation, and owner-controlled experimentation with devices you own and firmware copies you have lawfully obtained. This repository contains no Elektron firmware. Do not redistribute original or modified Elektron firmware images, and comply with applicable law and licence terms. Flashing modified firmware may render a device unusable.

License

MIT. See LICENSE.