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octatrack-kyoti-fw

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OT Kyoti FW — Octatrack OS reverse-engineering workspace. New features (Sidechain Compressor, Mute + FX Tails, BlackPyramids 303, Direct Jump, Varispeed + S900/950 and SP-1200 emulation); various QOL

octatrack-kyoti-fw is custom firmware for the Elektron Octatrack and Elektron Octatrack MKII, by @Zac-Kyoti. 17 stars on GitHub.

forElektron Octatrack,Elektron Octatrack MKII·by@Zac-Kyoti

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▐░░  O T   K Y O T I   F W   ·   custom Octatrack firmware  ░░▌
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OT Kyoti FW

Welcome Elektron fans. I'm Zac Kyoti, a musician and music tech hacker located on the US west coast. This repo contains knowledge and tools that may be used to research and explore modifications to the Octatrack stock firmware.

Design Philosophy: KYOTI firmware is designed as a set of new or extended features, QOL improvements, and bugfixes, not available in the factory firmware, which can be applied individually, in combination, or as a comprehensive build. All mods are designed to cleanly interlock. The KYOTI firmware design perspective comes foremost from a place of deep respect and appreciation for the architecture of these instruments before any mod is applied. As such, my approach is to make the modded instrument "feel" like stock — customizations appearing seamless, respecting existing UX/UI conventions, and (ideally) stage-ready and bug-free. KYOTI firmware is not about complete overhaul of the instrument's plumbing (there are plenty of other projects that do that, which you may consider combining with KYOTI); it's more about making the stock instrument the best version of itself it can be. Read on and enjoy!

The features list on the main branch will be updated as new builds roll out.

Influenced by the concepts of mxldyn/octamax by Maxolydian and other Octatrack RE projects — full credits in CREDITS.md.

Builds

You bring your own copy of the official OS 1.40C; the tools here turn it into a modified image, byte-for-byte reproducibly from your copy. No Elektron binary is included or distributed. Every feature is off by default — a freshly flashed unit behaves like stock until you opt in. The bug fixes are always on.

How to build: BUILD_KYOTI.md. How to flash, and how to get back to stock: FLASHING.md.

The WIP gate

Everything in this repo is work in progress until I promote it to final. Only final features are listed below. Every other build refuses to run unless you opt in:

KYOTI_ALLOW_WIP=1 python3 tools/build_<name>.py

An update to a final feature is work in progress too, until I promote it: the final build refuses to produce a changed image without the opt-in.

Features

Hardware testing is on my Octatrack MKI; nothing here has been tested on an MKII, but the MKII panel layout has been considered for every build.

MUTE_MODES

Choose how an audio track's mute behaves, in PERSONALIZE → MUTE MODE:

  • OT — stock
  • OTFX — a hard dry cut, but FX inserts ring out their tails and the sequencer keeps running underneath, so unmuting picks up where the pattern would have been
  • OTFX-T — the same, and new trigs stay suppressed until you unmute
  • DT-T — Digitakt-style: a sounding voice rides out its own amp envelope and FX, and only new trigs are suppressed

SOLO follows the same rule as a manual mute; CUE MUTES TRK stays a hard cut. The setting survives a power cycle.

Hardware: confirmed.
Final build: tools/build_mute_modes.py → OCTATRACK_OS1.40C_MUTE_MODES

DIRECT_JUMP_KYOTI

An optional immediate pattern change, toggled with [PTN] + [YES] (a toast confirms; it is OFF at every power-on). A cued pattern takes over on the next step instead of waiting for the current one to finish, locked to the master clock: it plays exactly where it would be had it been running since START, whatever its track lengths, scales or master settings. The Part, START SILENT and trig conditions change as on a stock pattern change, and the last MIDI Program Change sent always names the pattern that plays. The arranger and chains are untouched; with DIRECT JUMP off, pattern changes are stock. The image also carries BATCH_BUGFIXES' MIDI Plays-Free fix, which keeps a stock bug from feeding DIRECT JUMP a bad scale.

Hardware: confirmed: the clock-locked timing and the Part change. Not yet tested on hardware: MIDI tracks, Program Change on fast re-cues, START SILENT, and the trig-condition reset.
Final build: tools/build_direct_jump_kyoti.py → OCTATRACK_OS1.40C_DIRECT_JUMP_KYOTI

SIDECHAIN_COMPRESSOR

An external key input for the stock DynamiX COMPRESSOR, with a base-width key filter, on the effect's page 2:

  • MON — OFF (left) / ON (right): auditions the filtered key in place of the track; switching it, or changing KEY while it is on, fades instead of clicking
  • KEY — which of the eight audio tracks drives the compression, even while it is muted; one position per detent, also with the encoder pressed
  • KGN — the key's gain, about −24 to +24 dB; centre is unity
  • KBAS — the filter's base: a high-pass (18 dB/oct) at OFF or 20 Hz to 19.6 kHz, shown in Hz (40, 1.2k = 1.2 kHz)
  • KWID — the filter's width: a low-pass (12 dB/oct) set this many octaves above KBAS, 0.5 to 9.9 or OFF. With KBAS at OFF it counts up from 20 Hz: a plain low-pass

The base-width filter isolates the key — a kick's fundamental, for example, with KBAS cutting the sub-sonic rumble below it — which reduces distortion and keeps the compression smooth at short attack and release settings. The two knobs cannot cross.

The DSP space comes from SPRING REVERB, which leaves the FX2 list; a project that still uses it loads it as NONE.

Changed on 25 Oct 2026. MON shows OFF on the left and ON on the right (it was the other way round), and a COMPRESSOR saved with any earlier version comes up with MON OFF.

Changed on 22 Oct 2026. The base-width filter replaced the earlier one-knob KFLT, and page 2 was laid out again (it was RMS KEY KFLT KGN MON). A COMPRESSOR saved with the earlier version keeps its KEY, but its other page-2 values now land on different knobs: KGN gets the old KFLT, KBAS the old KGN, KWID the old MON, and MON comes up OFF. Such a project sounds different until you set KGN, KBAS, KWID and MON again. A COMPRESSOR saved on stock firmware is not affected.

The earlier version is still buildable, though not recommended: tools/build_sidechain_compressor_light.py builds it behind the WIP gate (KYOTI_ALLOW_WIP=1, see above); OS VERSION reads 140C_SCLT.

Hardware: confirmed.
Final build: tools/build_sidechain_compressor.py → OCTATRACK_OS1.40C_SIDECHAIN_COMPRESSOR

BLACKPYRAMIDS_303

A TB-303 voice as a track machine, shown as BLKPYRAMD, running on the Octatrack's DSP in 24-bit fixed point with its filter 4× oversampled at 176.4 kHz. Built on Open303 and recalibrated on the TB-303's own circuit against recordings of a real 303. It is the sixth row of a track's machine list (double-tap the track, or [FUNC] + [SRC] → MACHINE). One per DSP core: one on T1–T4, one on T5–T8.

  • SRC: PTCH (C0–C8, a semitone a step, shown as note names; FUNC + turn or push + turn steps by octaves, on every held trig too) · CUT (0–100 the real 303's whole range, evenly; 101–127 an octave beyond, where the top of RES is eased) · RES · ENV · DEC (50 ms–2 s) · ACC. RES, ENV and ACC cover the real 303's range; RES and ACC are spaced so every step does as much. SETUP: WAVE (saw → square, at equal loudness) · TUNE · SLID (slide time; default the 303's) · GATE (note length; default the 303's) · VOL (clean up to 64, driven above, rising smoothly; the default 99 adds about +5 dB).
  • Notes: each trig plays a note with the knobs at that step; p-lock PTCH for a melody.
  • Accent: p-lock ACC on the steps to accent, as a 303 marks them; the ACC knob scales every accent at once (127 plays the locks as set, 0 none; default 100). Accents in a row stack into the 303's rising sweep. A note without an ACC lock is never accented. A MIDI note with velocity above 100 is accented.
  • Slide: an OT slide trig glides into its note from the previous one, without a retrigger.
  • Ties: trigless locks and/or trigless trigs right after a note hold it. A trigless trig still resets LFOs and FX envelopes as on stock, so a trigless trig after a note also ties it.
  • Live: the track key, chromatic keys and MIDI notes play it, held while the key or note is down. TRIG + YES previews a step, and one-shot trigs play once until re-armed.
  • Chromatic mode: four octaves of absolute notes. [FUNC] + [LEFT] / [RIGHT] pick the octave (the page LEDs show it); trig 1 plays C1, C2, C3 or C4, [PAGE] the note above trig 16. SLOTS and SLICES modes have nothing to play here: their LEDs stay dark.
  • AMP, FX1, FX2, LFOs (PMTR lists the six SRC knobs), scenes, p-locks and trig conditions work as on any track.

Limits:

  • SPRING REVERB is removed: its DSP space holds the voice.
  • On a stock OS, the track opens as a FLEX track.

Credits: built on Open303 (MIT) by Robin Schmidt: its filter, oscillator and envelope algorithms. The recalibration takes its values from the TB-303's circuit (Roland's service notes, the x0xb0x schematics, Robin Whittle's notes) and Din Sync's recordings of a real TB-303. The machine registration follows repeat98's ANALOG BD for octabam. The Octatrack port, design, calibration and voicing are by Zac Kyoti, every choice made by ear, as is the hardware testing. What is Open303's and what is new, every voicing decision and full attribution: reference/BLACKPYRAMIDS_303.md and CREDITS.md.

Hardware: confirmed.
Final build: tools/build_blackpyramids_303.py → OCTATRACK_OS1.40C_BLACKPYRAMIDS_303

VARISPEED

Tempo-locked varispeed for STATIC and FLEX tracks. SRC SETUP's TSTR gets a fifth position, VARI: the sample plays dry, tape-style, its speed and pitch moving together and locked to the project tempo. RATE still applies. On TSTR AUTO, a sample whose TIMESTRETCH (audio editor → ATTR) is VARI plays the same way.

  • QUAN: on a VARI track PTCH becomes QUAN, a ratio on the tempo-locked speed: 1/2, 2/3, 3/4, 4/5, 1/1, 5/4, 4/3, 3/2, 2/1. Leaving VARI gives PTCH its value back.
  • Above twice the sample's own speed, it folds down an octave.
  • A sample or project tempo outside 30–300 BPM plays as TSTR OFF.

Hardware: confirmed.
Final build: tools/build_varispeed.py → OCTATRACK_OS1.40C_VARISPEED

VARISPEED_EMUS

VARISPEED with two sampler emulations. On a VARI track TSNS becomes EMUS, which picks the engine the track plays through:

  • OT: the Octatrack's own playback, as in VARISPEED
  • S950: the Akai S900/S950, 12-bit at its 40 kHz rate
  • SP12: the E-mu SP-1200, 12-bit at 26.04 kHz through its raw outputs, in stereo

A change of engine takes effect at the track's next trig. The engines run on the DSP. A change that would overload a DSP core is refused and shows MAX DSP: EMU LIMIT: an EMUS turn stops at the heaviest engine that fits, an FX type doesn't land, and a track coming onto VARI plays OT.

The DSP space comes from SPRING REVERB, which leaves both FX lists; a project that still uses it loads it as NONE.

Hardware: confirmed.
Final build: tools/build_varispeed_emus.py → OCTATRACK_OS1.40C_VARISPEED_EMUS

RELOAD_FROM_PROJECT

Reload one track's sequence from the CF card without stopping the transport:

  • [PTN] + [TRACK n] — reload that track's card-saved sequence, Part untouched
  • [BANK] + [TRACK n] — the same, and re-apply the saved Part

[CUE] + [TRACK n] stays stock. It reloads the pattern that is playing, on an audio or a MIDI track, and never restarts the sequence or the metronome. A toast confirms when the reload has finished, and says so if the trigs did not land.

Hardware: confirmed.
Final build: tools/build_reload_from_project.py → OCTATRACK_OS1.40C_RELOAD_FROM_PROJECT

QUANTIZE_LIVE_REC_TOGGLE

Reach the QUANTIZE LIVE REC setting from the front panel. Hold [REC] and tap [PLAY]: a toast shows the setting, LIVE REC: QUANTIZED or LIVE REC: UNQUANTIZED. Tap [PLAY] again while the toast is up to invert it; if PERSONALIZE is open, its check mark follows. Once the toast has gone (1 s), a tap just shows the setting again. The first [REC] + [PLAY] still starts live recording as on stock.

Hardware: confirmed.
Final build: tools/build_quantize_live_rec_toggle.py → OCTATRACK_OS1.40C_QUANTIZE_LIVE_REC_TOGGLE

ERASE_EMPTY_TRIGLESS_LOCKS

A trigless lock — a step with parameter locks but no audible trig — now disappears from the trig row once you erase its last lock, instead of staying lit. One placed deliberately with FUNC + TRIG is left alone.

Hardware: confirmed.
Final build: tools/build_erase_empty_trigless_locks.py → OCTATRACK_OS1.40C_ERASE_EMPTY_TRIGLESS_LOCKS

REC_TRIG_MUTE

Mute a track's recorder trigs without deleting them. Hold [TRACK] and press [REC]: that track's recorder trigs stop firing — a recording already running finishes — and a toast reads REC TRIGS MUTED. Press it again to bring them back (REC TRIGS UNMUTED). Each track keeps its own state: with several track keys held, each one flips (REC TRIGS TOGGLED when they end up mixed). The toast stays up while you hold the track key, up to 1 second, as QUANTIZE_LIVE_REC_TOGGLE's does, and closes when you let go. While a track key is held, [REC] does not switch grid recording; on its own [REC] works as on stock. It works on any screen and holds across pattern changes until you unmute; every track starts unmuted at power-on. A muted track shows two dots beside its play/stop icon at the screen edge (..■ / ..▶).

MIDI: CC 80 on a track's channel mutes it (1–127) or unmutes it (0); on the AUTO channel it acts on the active track. The keys send CC 80 (1 muted / 0 unmuted) on each held track's channel. Both need AUDIO CC IN / OUT on, as for every audio-track CC. [TRACK] + [YES] / [NO] arm and disarm recorder one-shot trigs as on stock.

Hardware: confirmed in KYOTI V1.6 ([TRACK] + [REC], the per-track toggle, the toast). MIDI CC 80 not specifically tested.
Final build: tools/build_rec_trig_mute.py → OCTATRACK_OS1.40C_REC_TRIG_MUTE

BATCH_BUGFIXES

Three fixes to stock bugs. Each has its own build.

  • MIDI_PLAYS_FREE_FIX — a Plays-Free MIDI track with trig quantize Direct and pattern scale Per Track no longer stalls after its first step on a manual trig.
    Hardware: confirmed. Final build: tools/build_midi_plays_free_fix.py
  • EMPTY_PATTERN_LED_FIX — a pattern whose only content is parameter locks now lights its grid LED under [PTN], instead of showing as an unused slot.
    Hardware: confirmed. Final build: tools/build_empty_pattern_led_fix.py → OCTATRACK_OS1.40C_EMPTY_PATTERN_LED_FIX
  • PART_CHANGE_CARRYOVER_FIX — after a pattern-triggered Part change, a track leaving PICKUP for FLEX no longer keeps playing the old Part's pickup loop, and a switch into a PICKUP track no longer marks the Part edited when nothing changed.
    Hardware: confirmed. Final build: tools/build_part_change_carryover_fix.py → OCTATRACK_OS1.40C_PART_CHANGE_CARRYOVER_FIX

Each feature + BATCH_BUGFIXES

One image per feature above, with all three BATCH_BUGFIXES folded in — ten images, for flashing a single feature without giving up the bug fixes. The features are not combined with each other.

Hardware: every ingredient is confirmed on its own; these combined images have not been flashed as such.
Final build: tools/build_bugbuilds.py → out/Bugbuilds/OCTATRACK_OS1.40C_<FEATURE>_BATCH_BUGFIXES

KYOTI V1.7

Every feature above except BLACKPYRAMIDS_303 and VARISPEED_EMUS, and all three BATCH_BUGFIXES, in one image. The boot splash and SYSTEM STATUS → OS VERSION read KYOTI V1.7. It replaces KYOTI V1.6 and earlier, and the withdrawn V1.0 (see below). A COMPRESSOR saved with V1.5 or earlier keeps its KEY; set its KGN, KBAS, KWID and MON again.

Hardware: confirmed (this combined image).
Final build: tools/build_kyoti.py → out/KYOTI/OCTATRACK_OS1.40C_KYOTI_V1.7

⚠️ Before you flash

KYOTI V1.0 (the earlier all-in-one image) is withdrawn as of 2026-10-06. It can crash the unit when an encoder is turned on an FX page set to NONE, and when T8's PLAYBACK or LFO page is shown with T8 as MASTER. If you flashed it, flash KYOTI V1.7 above, one of the single-feature builds, or stock OS 1.40C. None of those has this problem.

KYOTI V1.2 breaks PLATE REVERB (a damaged page, and its knobs do nothing). Flash KYOTI V1.7.

KYOTI V1.1–V1.6 change the stock DELAY's tone, and so does the VARISPEED_EMUS + BATCH_BUGFIXES image (BUG_VEM10) built before 2026-11-02: at most BASE / WDTH settings, the defaults included, the repeats are filtered darker than on stock. Flash KYOTI V1.7, or rebuild BUG_VEM10.

This is for personal study. Updating an Elektron unit with anything other than official firmware is risky: it puts the warranty in question and can leave the unit needing the bootloader recovery path. Nothing here is endorsed by, supported by, or affiliated with Elektron. If in doubt, don't flash — just read, disassemble, and learn.

Keep the official .syx on hand: [FUNC] + power on → [TRIG 3] recovers the unit even from a bad OS, because an OS update never touches the bootloader. Never cut power during UPDATING FLASH. The full procedure and recovery net are in FLASHING.md.