elektron-firmware-tool

Updated 3 weeks ago

About

An open-source command-line tool that looks inside Elektron OS files (.syx). It unpacks the firmware sections and, after you change something, packs them back into a valid file with correct checksums. Many firmware mods start here.

Highlights

Inspect: shows the layers and checks the stored checksums
Decompress: writes every section out as a raw file
Modify: replace a section or set the version string, the checksums are recomputed
Byte-exact repack as a self-check
Container formats ELE3, ELE2, ELEK, AD and the older Machinedrum / Monomachine format

What you need
A C compiler and make, plus an OS file downloaded from Elektron.

Good to know
Supporting a format does not mean every device and version has been validated. Flashing a rebuilt file is a separate decision: modified firmware can brick a device. The forum has a step-by-step tutorial for it, see the Discussion below.

README

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.


`transport.[ch]`	SysEx framing, 8-in-7 and 2+7+7 packing, decode and encode
`container.[ch]`	ELE3 / ELE2 / ELEK / AD / pre-ELE parsing and assembly
`aplib.[ch]`	the LZ77 + Elias-gamma codec, both directions
`integrity.[ch]`	SHA-256, HMAC-SHA256, CRC-32, checksums, key derivation
`firmware.[ch]`	the loaded-file model, and every integrity check in one pass
`report.[ch]`	all output formatting; recomputes nothing
`device.[ch]`	product ids and names
`util.h`	byte order, alignment, buffer limits
`main.c`	command line

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.

Pictures in the README load from GitHub.

Discussion

From the forum. Replies you write here are posted in the thread.

First Steps in Elektron Firmware Modding: Unpack, Edit & Repack

in Software General0 repliesOpen thread

Neutron

Administrator

09-30-2026, 12:16 AM#1

Unpacking and repacking Elektron firmware
A quick start with elektron-firmware-tool - https://github.com/mischa85/elektron-firmware-tool

Elektron ships OS updates as a .syx file. It contains the firmware, wrapped in SysEx messages, compressed and protected by checksums. The open-source elektron-firmware-tool by mischa85 unpacks the firmware and, after you change something, packs it back into a valid file.

It works with practically every Elektron device: Digitakt, Digitone, Syntakt, Analog Rytm/Four/Heat, Octatrack, Model:Samples/Cycles, Machinedrum and Monomachine. Every screenshot in this tutorial shows real output.

Quote:Please read first
The tool is unofficial and not affiliated with Elektron. Modified firmware can brick your device; everything you do is at your own risk. Only work with devices you own and with firmware you downloaded officially from Elektron. Please do not post .syx files on the forum; the firmware is protected by copyright.

All commands at a glance

Code:
elektron-firmware-tool -i OS.syx                            summary, check checksums
elektron-firmware-tool -i OS.syx -v                        detailed report
elektron-firmware-tool -i OS.syx -o folder                  extract all sections
elektron-firmware-tool -i OS.syx -d 3 -o folder            extract section 3 only
elektron-firmware-tool -i OS.syx -c 3 new.bin -o mod.syx    replace section 3, repack
elektron-firmware-tool -i OS.syx -r -o copy.syx            repack unchanged (self-test)

Extra options:
  -V 1.11                  set the version string (no longer than the old one)
  -l 0..3                  compression when packing: 0 = fast, 3 = small (default)
  --emit-container c.bin    also save the raw container to a file

1. Preparation

You need a C compiler and Git:

macOS: xcode-select --install
Linux (Debian/Ubuntu): sudo apt install build-essential git xxd
Windows: set up WSL with Ubuntu (wsl --install), then continue as on Linux. Work in your Linux home (~), not under /mnt/c, because one file name will contain a "?", which Windows does not allow.

Create a working folder. All commands in this tutorial run inside it:

Code:
mkdir -p ~/elektron-mods/original && cd ~/elektron-mods

Along the way you will add the subfolders extracted/ (unpacked), work/ (your changes), build/ (new .syx) and verify/ (checks).

2. Install the tool

Code:
git clone https://github.com/mischa85/elektron-firmware-tool.git
cd elektron-firmware-tool && make
cd ..
export PATH="$PWD/elektron-firmware-tool:$PATH"

① The program is built. There should be no warnings or errors.
② Makes the elektron-firmware-tool command available in the current terminal window. In a new window you need to run this line again, otherwise you get "command not found". To make it permanent, add it to ~/.zshrc or ~/.bashrc.

3. Get the firmware

Download the OS for your device from the Elektron website (Support & Downloads → your device → OS) and copy the .syx file into original/.

Tip:chmod a-w original/*.syx protects the original from being overwritten by accident.

Sound, pattern and project dumps are .syx files too, but they are not firmware. For those the tool reports "is not a recognizable Elektron OS .syx".

4. Inspect the firmware

Code:
elektron-firmware-tool -i original/Digitone_II_OS1.11.syx

① Device and OS version.
② The firmware's sections with their IDs. You need these IDs for -d and -c. "(raw)" means stored uncompressed.
③ All checksums match, the file is fine.

More detail with -v

Code:
elektron-firmware-tool -i original/Digitone_II_OS1.11.syx -v

① SysEx transport: the data is spread across 18,668 SysEx messages. Because MIDI carries only 7 bits per byte, it is "8-in-7" encoded. Every packet has its own checksum.
② Container (ELE3): model number, version and a checksum over the entire content.
③ Section table: position (off), packed length (clen) and load address in memory (dst) of each section.
④ MAIN OS is loaded at address 0x40000400. You will need this if you open the code in a disassembler later.
⑤ HMAC-SHA256: a signature over the whole container. The tool recomputes it automatically when repacking. We masked the key in the screenshot.

In short: mods almost always go into section 3 (MAIN OS), the actual operating system. Keep your hands off section 2 (bootstrap) and 4 (updater): the bootloader holds your device's recovery menu. The tool assigns the section names based on content. On other devices the IDs and sections can differ; the output of -i is always what counts.

Self-test (optional)

Code:
mkdir -p build
elektron-firmware-tool -i original/Digitone_II_OS1.11.syx -r -o build/repacked.syx
cmp original/Digitone_II_OS1.11.syx build/repacked.syx && echo "byte-identical"

-r repacks the file without changes. If you get exactly the same file back, the tool handles your firmware losslessly. With Digitone II firmware 1.11 it does.

5. Extract the firmware

Code:
elektron-firmware-tool -i original/Digitone_II_OS1.11.syx -o extracted

①.raw was already uncompressed and was copied 1:1. .bin was decompressed.
② Section 8 has no known name, hence the "?" in the file name. Best rename it right away:

Code:
mv "extracted/section_8_?.bin" extracted/section_8_unknown.bin

To extract single sections, use -d with the ID (repeatable). If the ID does not exist, the tool reports "no section id=…".

Code:
elektron-firmware-tool -i original/Digitone_II_OS1.11.syx -d 3 -o extracted

Important: don't edit anything in extracted/. These are your originals for comparison.

6. Edit a section

As an example, we replace the text UNTITLED in MAIN OS with ELEKMODS. This only demonstrates the workflow and was not tested on hardware.

Three rules

Only overwrite, never insert or delete bytes. The file must stay exactly the same size, otherwise every address after the change shifts.
Keep strings the same length and only use characters that already appear there (here: capital letters). The 00 byte at the end of the text stays in place.
Always work on a copy in work/.

6.1 Find the location

Code:
mkdir work
cp extracted/section_3_MAIN_OS.bin work/section_3_MAIN_OS.mod.bin
grep -obUa "UNTITLED" work/section_3_MAIN_OS.mod.bin
printf '0x%X\n' 2170423
xxd -s 0x211E27 -l 48 work/section_3_MAIN_OS.mod.bin

① Position (offset) of the text in the file, as a decimal number.
② The same offset in hex. This is how hex editors show it.
③ The text in the hex dump, with the 00 byte at the end.

6.2 Change the bytes
With a hex editor such as Hex Fiend (macOS), HxD (Windows) or ImHex (all systems): open the file, jump to offset 0x211E37, type the new text in overwrite mode, save.

Or in the terminal:

Code:
printf 'ELEKMODS' | dd of=work/section_3_MAIN_OS.mod.bin bs=1 seek=2170423 conv=notrunc
cmp -l extracted/section_3_MAIN_OS.bin work/section_3_MAIN_OS.mod.bin
xxd -s 0x211E27 -l 48 work/section_3_MAIN_OS.mod.bin

① Writes exactly 8 bytes at that position. Don't forget conv=notrunc, otherwise the file is cut off after it.
②cmp -l shows every changed byte (position counted from 1, values in octal). 8 lines means exactly 8 bytes changed and nothing else.
③ Double-check: ELEKMODS is in the right place.

7. Repack the firmware

Code:
mkdir -p build
elektron-firmware-tool -i original/Digitone_II_OS1.11.syx \
    -c 3 work/section_3_MAIN_OS.mod.bin \
    -o build/Digitone_II_OS1.11-mod.syx

① The original serves as the template (-i), section 3 is replaced with your file (-c 3), and the new file is written to -o. All other sections stay unchanged.
② The section is compressed again automatically.
③ Checksums and HMAC are recomputed.
④ The new file is smaller than the original. That is expected, because the tool compresses slightly better than Elektron. The content is still identical, see step 8.

Options when repacking

-l 0 to -l 3: compression level. The default 3 gives the smallest file (about 14 seconds here). -l 0 is roughly 18 times faster and about 3 % larger, good for experimenting.
Several sections at once: repeat -c, e.g. -c 3 a.bin -c 7 b.bin.
-V sets the version string. It must be no longer than the old one (here 4 characters like "1.11"), otherwise the tool reports "too long for field; unchanged".

8. Verify the result

Code:
elektron-firmware-tool -i build/Digitone_II_OS1.11-mod.syx
elektron-firmware-tool -i build/Digitone_II_OS1.11-mod.syx -d 3 -o verify
cmp verify/section_3_MAIN_OS.bin work/section_3_MAIN_OS.mod.bin && echo OK

① All checksums of the new file are valid.
② The section from the new .syx is byte-for-byte identical to your edited file, so packing and unpacking were lossless.

Done!build/Digitone_II_OS1.11-mod.syx contains your change, and all checksums match.

Questions, additions or your own findings are welcome in this thread.

elektron-firmware-tool is written by mischa85 and released under the MIT licence (GitHub). Neither the tool nor this tutorial is affiliated with Elektron. Elektron, Digitone, Digitakt and other product names are trademarks of Elektron Music Machines MAV AB.

Repositorymischa85/elektron-firmware-tool

Language: C
License: MIT License
Stars: 108
Forks: 17
Created: 07-22-2026
Last commit: 3 weeks ago

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