A six-track groovebox firmware for the M-VAVE FM-1 and SMK-37 Pro
synths and drums, patterns and songs, live performance, and a screen that shows what every control does

New in 1.4: Skiff on M-VAVE's SMK-37 Pro keyboard, REST in SONG, your own theme colours, each user sample's own level and sends, and an installer that carries on after a cut-off install · the release notes
New in 1.3.3: QUARK's scope as the tour video's event display, live from all six tracks, and fixes from your comments: HOME names the sound in LARGE too, PLAY says when it waits for an external clock, the installer says what it found · the release notes
New in 1.3: the FM-1's second core (BETA: 12 voices), MIDI LEARN and a channel per track, an INSERT effect, LFO sync, SPREAD and more from Felucca 1.6.1 · the release notes

▶ Watch the 1.3 tour on YouTube (3:38)

New to Skiff? Learn Skiff: the manual in chapters, each with a video that shows every press on the unit. Start with your first beat.
Try it first: Skiff in your browser, the firmware itself on a drawn FM-1, played with the mouse, a touch screen or the computer keyboard.

Skiff turns the FM-1 into a six-track groovebox: fourteen synth and drum engines with 148 factory sounds you can list by type (only the basses, only the pads), a 64-step sequencer with chords, ratchets, trig conditions and parameter locks, a shared pool of patterns played through per-track lists and scenes, and a performance layer for launching it all live. Every page draws what its knobs do, and holding HOME shows what every button, encoder and key does right there. FM6 sounds can be built from a bare sine on the unit itself, every operator's envelope drawn as it plays and coloured by how bright the FM makes it. A browser editor reaches all of it from a computer. The same firmware runs on M-VAVE's SMK-37 Pro keyboard, its pads a step grid and its faders a mixer: SMK37.md.

Skiff is free software, a fork of Felucca 1.1.5 by Hügelton Instruments: it keeps Felucca's engines, sound and file formats, so Felucca's sounds and projects load in Skiff. Skiff is not Felucca: please report Skiff's behaviour here, not in Felucca's Issues.

Custom firmware, at your own risk; the way back to the official firmware is below.

In the browser (Chrome or Edge on a computer): open the Skiff installer, connect the FM-1 by USB and follow it. The same page takes the FM-1 back to the official V15 firmware, saving a complete backup of your music first.

With Python 3: download skiff-1.4.fwsc from the latest release and, with this repository's tools/ folder,

pip install mido python-rtmidi
python tools/fm1_install.py skiff-1.4.fwsc

It takes about two minutes and the FM-1 restarts on Skiff.

Back to the official firmware: the installer page above, python tools/fm1_install.py FM-1.fwsc with M-VAVE's file, or M-VAVE's own updater. V15 writes its Bluetooth settings anew on its first start, so pair Bluetooth devices again if they don't connect.

On the SMK-37 Pro: the same installer finds the keyboard and picks its build (skiff-1.4-smk37.fwsc for Python). Two steps come first: M-VAVE's firmware V016 on the keyboard, and a backup of its flash, which holds the keyboard's own key calibration. SMK37.md has both, the way back and what to do if it does not start.

Edit from a computer: the Skiff Editor (Chrome or Edge, over USB MIDI).

Every factory sound has a type: BASS, LEAD, PAD, KEYS, PLUCK, DRUM or FX. When a track needs a bass, list the basses and step through them, across every engine, until one fits:

LIST: BASS: the basses of every engine, ENG saying whose each one is

Pick the track with ALGORITHM, say track 2. Tap SAVE for SAVE › PRESETS (turn SELECT to it if another SAVE page opens) and turn KNOB 4, LIST, to BASS. The list now holds only the basses: 19 of them, from eight engines. Turn PRESETS (or KNOB 1): each bass plays on the track as you reach it. One from another engine switches the track to that engine; its notes, its mix and its effects stay as they are. Stop on the one that fits. Gone past the sound you had? SAVE held brings it back: a run of PRESETS turns is one undo.

The LIST stays where you leave it, through a power-off too, and it is the unit's, not the track's. While it is on a type, the PRESETS knob steps through that type on HOME and the sound pages too, and the footer says BASS beside the engine, so you can browse from whichever page you are on. For track 3's pad: ALGORITHM to track 3, LIST to PAD. Back on ALL, PRESETS steps through all 148 again.

• FAV lists your favourites. On SAVE › PRESETS, turn KNOB 3, FAV, right to mark the sound playing, left to unmark it. Your own sounds (SAVE › USER) are listed on ALL and FAV.
• KNOB 2, ENG, jumps to the next engine's first sound, whatever the LIST.
• Tracks 5 and 6 leave PHYS and GRAIN out of every list, since they don't play them: 18 basses there.

A DRUM-X kit preset loads its whole kit, the project's one kit for every DRUM-X track; SAVE held brings the kit back too. Switching a track to DRUM-X keeps the kit the project has.

STEP: sixteen tiles, the notes on them; hold one and turn a knob to lock it	ROLL: the piano roll, chords and ties, the cursor step framed	Drum grid: the kit's eight lanes, accents bright, the white keys the steps
CHANCE: a step's chance, ratchet or FLAM, trig condition	AUTOMATION: every recorded move and lock, to edit, move or delete	SEQ TOOLS (hold SEQ): clear, reverse, shift, random, cook

SONG: each track's list of entries, the one playing filled, the next outlined	PERFORM (hold ARP): launch entries, stage mutes, recall scenes	PATTERNS: the pool of 64, what uses each one
GLO layer: levels, solos, mutes, FILL, tap tempo	GLOBAL: tempo and swing, the swung steps drawn	DUCK: a track dips under another's hits, the pump drawn over a bar
FX layer (hold FX): 14 effects on the white keys, an octave a row; cuts on the black	Effects held, a repeat waiting for its sixteenth

EDIT › OPERATOR and ALL OPS put every value of an FM6 patch on the unit's knobs: PRESETS picks the operator, SELECT its ratio, envelope, keyboard scaling, the algorithm, the pitch envelope and the LFO. INIT starts from a bare sine, and SAVE › USER keeps the result as a sound of its own. The graph, after an idea by Floyd Steinberg, is the note as the engine plays it: every operator's envelope, each carrier coloured along its length from cool (a sine) to hot (where the modulators make it bite).

OPERATOR: OP4's ratio; the carriers hot where it bites

ENV: the stage being turned, a filled handle

KEYS: the level across the keyboard

ALL OPS: the LFO's vibrato fading in

ENV	LFO DEST: the wave per destination	DELAY: the echoes	REVERB: SPRING's tail
ANALOG: the oscillator	FM6: its algorithm	DRUM-X: a kit sound, A beside B	SLICE: the slices on the wave
PHYS: the model sounding	VOICE: legato and glide	CHORD: the chord on the keys	MENU: five tabs of settings
DRIVE: the TYPE's curve, a sine through it	ENV 2: a second envelope, for the MOD matrix	LANES: a drum lane's level, tune and decay	CHORUS: FLANGER's comb
INSERT (1.3): FLANG's sweep	LFO 2 (1.3): synced to 1/4, one-sided	MIDI (1.3): LEARN, a channel per track	MIDI LEARN (1.3): a knob, then a CC

MENU › THEME: SKIFF (each track its own colour), HI-CON, PAPER, CRYPT (stone, amber and pixel letters, the graphs as ASCII art, torches and skulls), NEON (synthwave: chrome numbers, neon, the striped sun and the grid, a car on HOME's highway) and QUARK (particle physics: beams and collisions, nuclei, calorimeter towers):

CUSTOM takes your own colours from the web editor (a theme's five and the six tracks'), in the look of any of them. MENU › DISPLAY › PLAYHEAD LINE leaves HOME's playhead a line, without the torch, the car or the collision.

The Skiff Editor (web/editor.html, Chrome or Edge over USB MIDI) edits a connected FM-1 live: the sounds and their presets, the steps, the mixer, the Song tab (each track's list, the scenes, the pattern pool), the projects and their names, the DRUM-X kit and the MENU settings, with PLAY, STOP and REC at the top. It looks like the unit and follows its THEME, and sets THEME › CUSTOM's colours (Settings › Device display). It also keeps a library of sounds on the computer, imports FM6 patches from .syx files and saves complete backups.

The Sound tab: every parameter of the selected track	The Song tab: the lists, the scenes, the pattern pool
The Mixer tab: the six strips

• Six tracks, each its own engine and sound; 8 voices shared between them, 12 with the FM-1's second core (MENU › SYSTEM › CPU 2 CORES, BETA, 1.3). T5 and T6 play every engine but PHYS and GRAIN. ALGORITHM selects the track on every page; HOME, PERFORM, SONG and the MIXER show all six
• Fourteen engines (below), DRUM-X among them, each with at least 8 factory presets, 148 in all
• Sounds by type (1.2): every factory sound is a BASS, LEAD, PAD, KEYS, PLUCK, DRUM or FX sound; SAVE › PRESETS' LIST (KNOB 4) shows one type across every engine, and the PRESETS knob then steps through it on every page (Find a sound by type)
• FM6 from scratch (1.1): every value of an FM6 patch on the unit (EDIT › OPERATOR and ALL OPS), INIT a bare sine, the sound saved as a user sound; the operators' envelopes drawn as they play, each carrier shaded by its brightness, in every theme's own look
• Every page shows what it does: the four knobs as cards across the top, and a graph of the page below: the envelope, the LFO per destination, the delay's echoes, the reverb's tail, the swing grid, the glide, the oscillator and filter, the arpeggio. Hold HOME (SHIFT) and a map shows what every button, encoder and key does on that page
• Sequencer: 64 steps a track with chords, ties, accent, slide, velocity, per-step chance and trig conditions (1:2, 3:4 ..), ratchets and FLAM, NUDGE (a step early or late, in 64ths), a step's own GATE, play direction (FWD, RVRS, PING, RAND); SEQ › STEP as 16 tiles, the piano roll (ROLL), a drum grid (white keys steps, black keys lanes; a step's chance, ratchet and condition cover every hit on it); live loop recording with overdub, FEEL (recording keeps where you played), step recording, count-in and click. While playing, the step pages follow the playhead past step 16 (1.3); MENU › STEP PREVIEW sounds the step KNOB 1 lands on in the piano roll (1.3); QUANTIZE SEQ+T transposes the sequencer's notes by TRANSP before it snaps them to the scale (1.3)
• Patterns and songs: 64 patterns shared by every project; each track has a list of 16 entries (A–P), each a pattern played REPS times; SONG plays each track down its list. Patterns keep themselves: no save needed
• PERFORM (hold ARP): launch any track's entries from the white keys, stage mutes on the black ones, on the next LOOP, BAR, BEAT or NOW; 16 scenes (every track's entry and mute), SAVE held + a key stores one; throws on KNOB 1–4 (CUTOFF, REVERB, DELAY, DIST) that glide back over a bar
• TAKE (SHIFT + SAVE): keep the last loop you played, notes and knob moves, on the track, after the fact
• Undo: SAVE held, 8 levels across the tracks (sound loads, takes, clears, tools, recording passes, automation edits); OCT− and OCT+ step through them while the undo box shows
• Parameter locks and automation: hold a step and turn a knob to lock it; knob moves recorded live; SEQ › AUTOMATION lists them all to edit, move or delete
• SEQ TOOLS (hold SEQ): CLEAR, REVERSE, SHIFT < / >, RANDOM, COOK, and (1.3) EUCLID (hits spread over the steps, rotated; OCT+ applies), DOUBLE and HALF (the length and the steps with it); on a drum track BEAT and each lane's tools
• MOMENTARY (1.3): hold LFO and turn knobs on HOME, a sound page, an FX page or the MIXER: let go and the values spring back (OCT+ keeps them), not recorded
• Lane mutes (1.3): on a DRUM or DRUM-X track the EDIT layer's black keys 1–8 mute its lanes
• DUCK (FX › DUCK): a track dips under another track's hits, the sidechain pump
• Effects: per track DIST, in four types on FX › DRIVE (SOFT, HARD, FOLD, BITS) with a TONE, and the SLICER; the buses on GLO: chorus (CHORUS, FLANGER or PHASER, with FEEDBACK), delay and reverb (ROOM, SPRING or a stereo HALL); the FX layer (hold FX): fourteen effects on the white keys and cuts on the black (the keys); new in 1.2: DRIVE's types and TONE, the chorus's modes, HALL, and GATE, DUB, FLANGE and VINYL on the FX layer; new in 1.3: FX › INSERT, a second effect per track after DRIVE (SOFT, HARD, FOLD, FUZZ, CRUSH, PHASR, FLANG or CHOR, its A, B and C named by the type, INSERT 2's MIX), and the delay's dotted times (1/8D, 1/16D, 1/4D)
• Quick layers: hold FX, GLO, SEL, EDIT, ARP or SEQ for its map on the keys and knobs; SHIFT + the button, or the button held + HOME (1.2.1), keeps it open. The GLO layer: solos, mutes, FILL, tap tempo
• DRUM-X (from JIANT FM): a synthesized kit of 8 sounds, each with an A and a B patch and MORPH between them, one kit per project, edited a sound at a time on EDIT › SOUND; eight kits come as presets (1.2), each loading its own (FACTORY, DEEP, CLICK, INDUSTRIAL, SOFT, GLITCH, TRIBAL, LASER)
• Chord keys, arpeggiator, scales: in-key chords with voicings; an arpeggiator with 14 modes, CHANCE, SWING and HOLD; 16 scales with a white-key mode; MONO, LEGATO, UNISON and glide
• Modulation matrix: 4 slots a track; the sources the LFO, ENV and a second envelope of its own (ENV › ENV 2, 1.2), velocity, the key, a random value, MIDI controllers and (1.3) S&H and SLEW (a random value a cycle of the LFO, stepped or gliding); (1.3) the destinations DEPTH (the LFO's depth: MODW › DEPTH is a mod-wheel vibrato), and VEL and TIME to humanize: each note's velocity, each step a little late
• LFO 2 (1.3): SYNC to a note value of the tempo (4 bars to 1/32), TRIG FREE (a note leaves its phase), POLARITY UNI (one-sided); ENV SYNC (ENV DEST, 1.3): ATTACK, DECAY and RELEASE as note values, 1/64T to 4 bars
• SPREAD (EDIT › VOICE 2, 1.3): a POLY or UNISON track's voices left and right of PAN in turn
• Presets and projects: factory presets, 32 user sounds and 4 projects, named on the device; SAVE › PROJECT loads, saves, renames and deletes them, and NEW on an empty slot starts a blank project (1.2.1); the music comes back at power-on (RESTORE LAST, an autosave of its own)
• Screen and LEDs: the BLOCKS look in Barlow Condensed with Fukiai icons; six themes; MENU › LARGE for tall cards; messages say the way out; idle buttons glow, what can be pressed breathes, never blinks
• USB and MIDI: class-compliant MIDI in and out, TRS MIDI in, a stereo USB audio input to record the master on a computer; channels 1–6 play tracks 1–6 (MENU › MIDI IN CH1-6), and (1.3) each track can listen on a channel of its own (MENU › MIDI › T1–T6 CHANNEL); clock from internal, USB or TRS. MIDI LEARN (1.3): MENU › MIDI › MIDI LEARN, turn a knob, send a CC: the controller sets that parameter, up to 10 of them; Program Change (1.3) loads the track's nth preset. Standard CCs, each on the track its channel plays (recorded as automation while it's armed): CC7 LEVEL, CC10 PAN, CC5 GLIDE, CC73 ATTACK, CC75 DECAY, CC72 RELEASE, CC74 the engine's brightness (ANALOG's CUTOFF ..), CC71 its resonance, CC91 REVERB, CC93 CHORUS, CC94 DELAY; CC1 mod wheel and CC11 expression (MOD sources), CC64 sustain

The notes live in patterns, and a project says which ones each track plays:

• A pattern is a track's notes exactly as they play: all 64 steps whole, LENGTH, DIV, SWING, GATE and DIR, and the track's automation and locks. The sound is not part of it. There are 64 of them, 01–64, in one pool that every project shares (SAVE › PATTERNS); entries naming the same pattern share it, and COPY gives an entry its own.
• Each track has a list of 16 entries, A–P. An entry names a pattern (or none) and its REPS, the passes it plays (1–16). A track is always on one entry, and HOME, the SEQ pages and the keys edit that entry's pattern.
• Nothing to save: what a track has is kept as the pattern it is on, written to flash at the quiet autosave (and before a project save or load, or a backup).
• Playing an entry (SEQ › SONG's OCT+, a PERFORM key, a scene, or a double-click in the editor) switches at once when stopped, and when playing at the LAUNCH point: the track's pass end (LOOP), the next BAR, BEAT, or NOW.
• SONG ON: while playing, each track moves to its next entry once the current one's REPS are played, at its own pass end; an empty entry between two patterns is a rest, silent for its REPS passes of the track's length (1.2.1); the empty ones after the last end the list, and after the last comes the first. KNOB 2 also picks REST for an entry anywhere in the list, so a track can start later or end sooner without an empty pattern. Tracks of different lengths move on at different times. SONG OFF: each track loops its entry. GLO + PLAY starts every track from its first entry.
• Scenes (16, in the project) keep the entry each track is on and every mute; SAVE held + a key stores one, a key recalls it, staged so that it all lands together.

The black keys' legends are M-VAVE's: docs/keystrip.pdf is a strip to print (at 100 %) and lay by the keys, with what each key is in Skiff.

• Tap a page button for its pages (again, or SELECT, for the next one); every family reopens the page you left
• HOME goes home. Held, it is SHIFT: its map shows what every control does on the page; let go alone, the MENU opens
• Hold FX, GLO, SEL, EDIT, ARP or SEQ for its layer; SHIFT + the button (or the button held, then HOME) keeps it open (the header says LOCKED), the button closes it. A locked FX layer latches its effects
• SAVE tapped: its pages (PRESETS, USER, PATTERNS, PROJECT); held: undo. SHIFT + SAVE: TAKE
• REC arms or disarms the selected track the moment it is pressed. SHIFT + REC opens the REC layer: F3 held clears the track's sequence, then CLICK, COUNT-IN, CLICK LEVEL, FEEL
• EDIT opens the EDIT pages everywhere; on STEP and ROLL with REC armed it clears the cursor step
• SELECT turns the pages of a family; GLO + SELECT sets the tempo (MENU › BPM LOCK, on by default)
• PRESETS changes the sound; on the step pages it moves the cursor, on lists it picks. With SAVE › PRESETS' LIST on a type (BASS, PAD ..) it steps through that type only
• On action pages and in dialogs, OCT+ does it and OCT− goes back
• Hold a step on SEQ › STEP and turn KNOB 1–4 to lock those parameters on that step
• Save a sound: stop, tap SAVE (USER), pick a slot with KNOB 1, OCT+, name it with the keys, OCT+

Hold FX and press a key: its effect plays while the key is held (SHIFT + FX keeps the layer open, and then a key latches its effect). Effects of different kinds stack; of the ones that play back what was just heard (REPEAT, REVERSE, TAPE STOP, FREEZE, OCT UP and DN, FLANGE, VINYL) the last one pressed plays, and letting it go returns to the one held before.

REPEAT and REVERSE start on the next sixteenth. The black keys F#3, G#3, A#3, C#4, D#4 and F#4 cut tracks 1–6 while held. KNOB 1–4 are the layer's macros: FILTER (left a low-pass, right a high-pass), CRUSH, THROW (the mix into the delay and the reverb) and DEPTH, how much of the effect you hear (with OCT UP or DN, its shimmer instead; with GATE, how deep it cuts).

In the order the device lists them:

• ANALOG: virtual analog; two oscillators, noise, drive, resonant low-pass filter; (1.3) WAVE SYNC (a hard-synced saw the envelope sweeps) and SUB (a saw on a square an octave down)
• FM6: classic 6-operator FM (Dexed-based): 32 algorithms, a full patch per track, every value of it editable on the device (EDIT › OPERATOR and ALL OPS: the operators' envelopes drawn as they play, each carrier shaded by how bright the modulators make it) or in the web editor (which imports .syx files); INIT starts from a bare sine; macros on the device, an algorithm chart; SLOT picks a factory patch (F1–F8) or the track's own (OWN)
• PHASE: phase distortion (ported from CrispyZebra); (1.3) FOLD, a wavefolder
• LOFI: chiptune; pulse, triangle, saw, noise and a 4-bit wave RAM, stepped envelope, sweep, arpeggio
• SAMPLE: multisampled instruments and 3 user sample slots, each sample with its own level, reverb and delay (EDIT › SAMPLES)
• VOICE: formant oscillator, sung vowels
• TRIO: 3 oscillators with ring modulation and sync, multimode filter
• WHEEL: tonewheel-style organ; drawbar registrations, percussion, key click, drive, rotary speaker
• GRAIN: granular textures from the built-in samples or a user slot
• PHYS: physical models: modal resonators, strings, struck membranes, sympathetic strings
• NOISE: noise from analog to digital: colours, crackle, shift-register and metallic tones
• SLICE: two drum breaks, a piano note (all built in) or your own sample cut into slices, one per key; set the slices by hand on the SLICES page
• DRUM: an 8-lane kit of Felucca's own drum voices on the General MIDI key map. KIT picks the standard kit or one of five virtual-analog (VA) kits in the manner of classic analog drum machines (the numbers are a hint), every lane its own voice: 80 (deep sine kick with a long decay, noisy snare, six-square hats), 10 (swept kick, white-noise snare, long-tailed claps, a cymbal), 66 (soft round kick, bright snare, noise hats, a conga), 55 (dropping kick, high metal hats, a metal bell) and 77 (swelling kick, multi-burst claps, claves, a cymbal), and (1.3) DEEP, TIGHT and PERC, put together from those five's pieces. All of them are synthesized, no samples, and each has presets (BOOM KIT, CRISP KIT, RHYTHM BOX, ELECTRO KIT, STUDIO KIT ..). EDIT › LANES sets each lane on its own: KNOB 1 the lane, KNOB 2 its level, KNOB 3 its tune (±12 semitones), KNOB 4 its decay (0 as the kit has it)
• DRUM-X: a synthesized 8-sound kit from JIANT FM, after the idea of Sonic Charge's Microtonic: each sound an oscillator (SIN, FM, MTL, BEL) with a pitch envelope and filtered noise, two patches A and B with MORPH between them; one kit a project, edited on EDIT › SOUND, a sound at a time. Its presets FACTORY KIT, DEEP KIT, CLICK KIT, INDUSTRIAL, SOFT KIT, GLITCH KIT, TRIBAL KIT and LASER KIT each load a kit of their own (SAVE held brings the one before back); OWN KIT and HADRON KIT keep the project's kit

SLICER (FX › SLICER, every track): a tempo-synced 16-step gate or stutter, with 16 patterns.

Hold HOME and let it go for the menu. It is in five tabs: DISPLAY (THEME to LEDS, SCREEN OFF, HINTS), CONTROL (HOLD to BPM LOCK, SCALE LEDS, STEP PREVIEW), AUDIO (SPEAKER EQ, USB LEVEL, CLICK, CLICK LEVEL, COUNT-IN, TUNE), SYSTEM (USB SERIAL, RESTORE LAST, CPU, HARDWARE CALIBRATION, RESET SETTINGS, ABOUT) and MIDI (CLOCK, MIDI IN, MIDI LEARN, LEARN CLEAR, T1–T6 CHANNEL; its rows scroll, six at a time). ALGORITHM moves between the tabs and PRESETS through the rows of one; any of KNOB 1–4, or OCT+ / OCT−, changes the value (OCT+ opens HARDWARE CALIBRATION and ABOUT, starts MIDI LEARN and clears what it learned); press HOME to close the menu. RESET SETTINGS puts every setting back as a new unit has it. The web editor's Settings tab reads and changes them too.

On the SCALE page (the SEL button), set QNT to WHITE to play the selected scale using only the white keys (SNAP keeps every key and rounds it down to the scale). C4 plays ROOT; consecutive white keys play consecutive scale notes above and below it. Black keys are silent, including during live recording and step entry. TRN transposes the resulting notes; the octave buttons shift them by full octaves. Set QNT to OFF for the normal chromatic keyboard. QNT SEQ snaps the keys like SNAP and also maps the sequenced notes onto the current ROOT / SCALE as they play (the steps are not changed; drum kits are never quantized).

Scales: chromatic (CHR), major (MAJ), natural minor (MIN), Dorian (DOR), Mixolydian (MIX), major pentatonic (PEN), minor pentatonic (MPEN), harmonic minor (HARM), Phrygian (PHRY), Lydian (LYD), Locrian (LOC), ascending melodic minor (MEL), minor blues (BLUES), whole tone (WHOLE), half-whole diminished (DIMHW) and whole-half diminished (DIMWH). Scales with other than seven notes continue across the white keys without repeating notes. Drum kits and incoming MIDI keep their own note mapping. Press SEL again for the CHORD page: CHRD picks the chord keys (OFF, the scale's triads or sevenths, or a fixed shape) and VOIC the voicing.

BUILDING.md: the toolchain, the JieLi AC79 SDK the package needs three files from, ./build.sh (writes build/felucca.fwsc) and tests/run_tests.sh, the host tests every change keeps passing. How every screen and control behaves, rule by rule: DESIGN.md. The editor's protocol: web/EDITOR_PROTOCOL.md. Contributions: CONTRIBUTING.md.

M-VAVE SMK-37: BOARD=smk37 ./build.sh (MODEL=elite, MODEL=mke for the other two names): see SMK37.md.

On the SMK-37: SMK37.md.

The screen says UPDATE MODE, or stays black while a computer sees a USB MIDI device named "Felucca Update": an install was cut off, and the FM-1 waits in Skiff's update loader at every power-on. Nothing is lost. Connect it by USB and run the Skiff installer again (or python tools/fm1_install.py skiff-1.4.fwsc): it finishes the install. If the installer can't find it, plug the FM-1 straight into the computer: a USB hub or USB-sharing software can lose it when it switches to update mode. M-VAVE's own updater does not see the FM-1 in this state. (Since 1.3.2 the loader says UPDATE MODE on the screen; one an older Skiff left there keeps it black.)

A computer sees a USB disk named WL82 UBOOT1.00 (or WL80UBOOT, a USB mass-storage device with ID 4C4A:8057): that is the chip's built-in boot mode, and the FM-1 can be brought back:

• First try another USB data cable, and close every other app that uses MIDI, then run tools/fm1_install.py again: it finishes an interrupted update.
• If it stays in boot mode, FM-1 Transporter reads and writes the FM-1's flash from a Mac through a Seeed XIAO RP2040 (three wires to the FM-1's USB lines). Back up the flash first, then write the official firmware (M-VAVE's FM-1.fwsc). On Windows and Linux, jl-uboot-tool reads and writes it over the same USB cable, as SMK37.md describes for the keyboard (the FM-1's flash is 1 MiB too).

A computer sees nothing at all: try another USB cable (a charge-only cable has no data lines) and another port, with the FM-1 charged, then restart the computer: Windows can leave a USB port dead after a device in boot mode goes away. FM-1 Transporter (above) reaches the chip's boot mode by itself.

Skiff stands on Felucca. If it is useful to you, support Felucca's author: sponsoring on GitHub or a donation on itch.io.

• Felucca by Hügelton Instruments (Leo Kuroshita, @kurogedelic): the firmware Skiff is built on, and in 1.3 the features of its 1.2 to 1.6.1 (LFO 2, the INSERT, MIDI LEARN and the channels, SPREAD, ENV SYNC, the MOD additions, EUCLID, and more); the PHASE engine's waveforms (a C port of the oscillator of CrispyZebra, GPL-3.0); the DRUM voices and kits; the Hügelton Sample Pack (the drum samples, GPL-3.0-only, not CC0); the Fukiai icon font (MIT)
• Fonts: Barlow Condensed by The Barlow Project Authors (the screen and the editor), SIL OFL 1.1; Inter Tight by The Inter Project Authors (the control card), SIL OFL 1.1; the browser emulator's labels: DotGothic16 by The DotGothic16 Project Authors, SIL OFL 1.1
• Samples: Versilian Studios VSCO-2 Community Edition and VCSL, CC0 1.0: the SAMPLE sets, also SLICE's PIANO (attribution)
• SLICE's BREAK and FUNK: made with YuE2 by Multimodal Art Projection (how)
• VOICE engine: after klattsch by Tony Gies (MIT); formant data from Klatt (1980) and Hillenbrand et al. (1995)
• PHYS engine: models ported from DaisySP by Electrosmith and Emilie Gillet (MIT) and from Emilie Gillet's eurorack code (MIT)
• FM6 engine: msfa from Dexed by Google Inc. and Pascal Gauthier (Apache-2.0)
• DRUM-X engine: from JIANT FM by juanjiant-bit (GPL-3.0-only), after the idea of Sonic Charge's Microtonic
• Browser emulator: after X0X by charlesvestal (GPL-3.0), a Felucca fork whose browser build showed the way
• Second core: as Felucca 1.6.1 has it, its start code from X0X, after Melodee by keremimo and with Jangada's measurements and hardening by zednaked (all GPL-3.0); its host tests by gospodindilly-ops
• 320 MHz (MENU › SYSTEM › CPU CLOCK): the switch from fm1-clk320-probe by curist (MIT), after the JieLi AC79 SDK's clock code (Apache-2.0)
• The SMK-37 build: the board layer of genkigenki's SMK-37 port of Felucca (GPL-3.0-only: the input, screen, pad LED, flash map, update and installer parts), and the SMK-37 hardware notes of their fm1-to-smk37 kit
• Package format and boot files: JieLi AC79 SDK (Apache-2.0; three of its files are in every package, none in this tree)
• Contributions to Felucca: keremimo (white-key scales, #2), ChanceTheMaker (TRS MIDI, bend, sustain and clock, palettes, favourites, editor display settings: #8, #10, #11, #12), andreahaku (sample recording and trim, #29; SLICE manual slices and tests, #27, #22), spinkham (the boot fix for 0.9 projects, #111), zednaked (ratchets, #100), jasonpersinger (the ROOM reverb click fix, #121), renebohne (MIDI Program Change, #179)

Free software: GPL-3.0-only, the Hügelton Sample Pack included. Skiff is a modified version of Felucca; its changes are marked (Skiff) in the sources. The bundled fonts and the ported DSP keep their own licences (LICENSES/); details in LICENSING.md.

M-VAVE, FM-1 and SMK-37 are trademarks of their respective owners. Skiff and Felucca are not affiliated with or endorsed by them, and Skiff is not made or endorsed by Hügelton Instruments.

Copyright (C) 2026 Leo Kuroshita (@kurogedelic), Hügelton Instruments (Felucca)
Copyright (C) 2026 illuminus5 (Skiff)