SY FM4 for Elektron Syntakt

A four-operator FM machine for the Syntakt's digital tracks. It upgrades SY TONE in place, so existing projects keep sounding the same: ALGO 0 is SY TONE, and ALGO 1–11 are four-operator algorithms. The extra parameters go on a second SYN page.

Target: Syntakt OS 1.40A only (SHA-256 266a5a30…2b5828). Ports to 1.41 and 1.42 aren't done yet (see Porting).

Not affiliated with Elektron. Modified firmware can make your device unusable and may void your warranty. This repository contains no Elektron firmware: the patchers read your own copy of the stock OS and check the SHA-256 of every byte range they overwrite. Don't share built .syx files.

What you get

• SYN 1/2: SY TONE's page, unchanged: TUNE RATIO PNCH DEC / FDBK MOD MENV OVER.
• SYN 2/2: press SYN again:
  • top row (operator 3): ALGO RAT3 LEV3 DEC3;
  • bottom row (operator 4): DET RAT4 LEV4 DEC4.
• ALGO 0: SY TONE itself. Its output is sample-identical to the stock machine.
• ALGO 1–8: the classic Yamaha 4-op set.
• ALGO 9–11: tree, diamond and ring.
• DET detunes operators 2–4 by ±16 semitones, with fine steps.
• Page 2/2 is saved with the sound and p-lockable. A sound saved by a stock OS opens with page 2/2's defaults, i.e. as SY TONE.

Status

Tested on a real Syntakt (OS 1.40A):

• the update installs and SY FM4 runs;
• every parameter works, including p-locks on trigs;
• load test: 8 tracks of SY FM4 sustained for 47 s, recorded clean (no clicks, dropouts or clipping).

Verified in an emulator (digiemu with a Syntakt port) but not yet on the device:

• sound and pattern-lock save/reload, using the firmware's own serialisers;
• CPU cost: SY FM4 uses about 8.9k cycles per voice per block, comparable to the stock engines (7.2k–9.8k). With 8 voices on SY FM4, the voice CPU stays at about 66 %.

Build

You need:

• your own Syntakt_OS1.40A.syx, downloaded from Elektron;
• elektron-firmware-tool;
• a ColdFire cross gcc (m68k-elf-gcc, or CROSS=m68k-linux-gnu- for the Debian/Ubuntu package);
• python3 and make.

EFT=/path/to/elektron-firmware-tool ./build.sh path/to/Syntakt_OS1.40A.syx
# -> out/Syntakt_OS1.40A-syfm4.syx

The output is deterministic. The build verified here has SHA-256 252e12ea25773178ecaeab45c4aa59871a9a50e74bf47cc44c85b23d670e4509, the image that was tested on hardware.

To run the engine's host tests (a double-precision reference, structural checks, and a WAV per algorithm):

make -C engine test

Flash and recover

• Flash: Elektron Transfer, Drop page, as for an official OS.
• Go back: flash the stock 1.40A the same way.
• If the unit doesn't boot: hold [FUNC] at power-on, then [TRIG 4] (OS UPGRADE). Send the stock OS from Transfer's Legacy OS upgrade page over MIDI DIN; USB doesn't work in this mode. Know this procedure before you flash.

Layout

Porting

Everything above the engine is tied to 1.40A addresses. Two lists hold them:

• the #defines and comments in engine/syn/fm4_syn.c and engine/main/main_fm4.c;
• the constants and put() sites in the two patchers.

For 1.41/1.42, map each one, for example with the per-region offset approach in SyntHack's os-1.42 branch (tools/build/osver.py). Then re-check:

• Section 7's size limit (0x60000 − 5 bytes in 1.40A).
• Main OS layout: the bss end and the 0x47000000 load address.
• Descriptors 1–5 and 12–14. Page 2/2 reuses these "Error" placeholder descriptors. In 1.40A they carried MIDI CC placeholders (CC 1, 2, 6, 7, 10, 120, 121, 123), which SY FM4 removes. SyntHack notes that logical ids 1–5 and 11–18 are tied to MIDI CCs, so pick placeholders that are really free in the target OS.

License

MIT, see LICENSE. Elektron and Syntakt are trademarks of Elektron Music Machines; this project isn't affiliated with or endorsed by them.