Skiff

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 2.1.1: a drum struck again while it still rings starts without a click: tom rolls, ratchets and the long-decay kits · the release notes
New in 2.1: chord follow, a bass line or an arp that moves with another track's chords, and QUANTIZE SOLO, chords on the white keys and a tune on the black ones · the release notes
New in 2.0.3: KBD HOLD, whole chords into the arpeggiator on MONO sounds, sampled notes struck again without a click, Learn's videos re-made on 2.0, and fixes from your issues · the release notes
New in 2.0.2: notes up to 128 steps long, the way back to the official firmware takes V16 too, and fixes from your issues · the release notes
New in 2.0.1: fixes from your issues: FM6 sounds from DX7 banks no longer crackle, OCT+ in the EDIT layer turns every drum lane back on, and the editor finds the unit on a Mac too · the release notes
New in 2.0: NOTES and FEEL, notes that overlap with lengths of their own, chains, songs that play once and change sounds, drum lanes panned and your own drum kits, one mute and one MOD page, and new save formats with room to grow · the release notes
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: 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, notes of any length that overlap, 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.

Install

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 firmware (V15 or V16: the version it had before Skiff), saving a complete backup of your music first.

With Python 3: download skiff-2.1.1.fwsc from the latest release and, with this repository's tools/ folder,

pip install mido python-rtmidi
python tools/fm1_install.py skiff-2.1.1.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. An FM-1 that ran V16 before Skiff goes back to V16, one that only ever ran V15 to V15: its start-up part decides, and the installer says which one it needs. M-VAVE's download page has given V16 since October 21 (Skiff 2.0.2 and later; done on a unit: back to V16, then on to Skiff again); V15 is in M-VAVE's fm1_open repository as sdk/firmware/FM-1_015.fwsc. The official firmware 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-2.1.1-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.

Updating to 2.0 from Skiff 1.x or Felucca: 2.0 reads what Skiff 1.0 and later saved, and keeps it in newer formats from then on. The installer page first takes a complete backup and saves it to your computer (Skiff-backup-DATE.json: keep it, it is the way back). After the install it converts what 2.0 can't read as it was (Felucca's projects and user sounds, DIGITAL sounds, the oldest formats) and writes only that back, with a list of what it converted and of anything with no place in 2.0.

• fm1_install.py converts nothing. 2.0 shows a slot it can't read as OLD FORMAT and keeps it. In the Skiff Editor, take a backup and restore it: the Restore converts it.
• A project the converter couldn't give patterns to (the pattern pool full) also stays OLD FORMAT: free some in SAVE › PATTERNS, then take a backup and restore it.
• The way back to 1.x: install 1.4.x, then restore the dated backup in the Skiff Editor. 1.x doesn't read what 2.0 saves: such projects and user sounds look empty there (their bytes stay until saved over), and its settings start at their defaults.

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

At a glance

A tour

Find a sound by type

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.

Sequencer

NOTES: the piano roll; the knobs move the selection, here step 5's chord, as one	Notes that overlap: a long note under the line, each note its own length	Drum grid: the kit's eight lanes, accents bright, the white keys the steps
FEEL: sixteen tiles, each step's chance or condition, ratchet or FLAM, nudge, accent and slide	AUTOMATION: every recorded move and lock, to edit, move or delete	SEQ TOOLS (hold SEQ): clear, reverse, shift, random, cook

Patterns, songs and performance

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; the tracks' mutes on the black	Effects held, a repeat waiting for its sixteenth	Chains (2.0): entries on CHAIN, one box each, played and edited as one pattern
An entry's sound (2.0): its tile's corner cut off, the footer naming it; loaded as the track comes onto the entry	LANE MIX (2.0): each drum lane's level and pan	Your own kit (2.0): KIT USR1, the slot's samples on the lanes; BELL has none, dimmed

FM6 from scratch

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

Sound: every page draws what it does

ENV	MOD: where the LFO and the envelope go, a grid over the four slots	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

Themes

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 web editor

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. Its Samples tab fills the user sample slots from WAV files or a recording; (2.0) its Drum kit switch makes a slot a kit for DRUM: a WAV a lane, each with a level, the files' levels to each other kept. On 2.0 its Restore converts a backup of before (Skiff 1.x, Felucca) first, and lists what it converted.

The Sound tab: every parameter of the selected track	The Song tab: the lists (a chain boxed, entries with a sound), the scenes, the pattern pool
The Mixer tab: the six strips	The Samples tab (2.0): USR1 as a drum kit, a WAV a lane

Features

• 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, MOD's routes as a grid, 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, 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); 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 the cursor lands on (1.3); QUANTIZE SEQ+T transposes the sequencer's notes by TRANSP before it snaps them to the scale (1.3)
• NOTES and FEEL (2.0): two step pages, PRESETS the cursor on both. SEQ › NOTES, the piano roll, edits a selection as one, the cursor's step or a range (SHIFT + PRESETS): PITCH (along the scale), START, LENGTH and VELOCITY. Notes overlap, each with its own length (1–99 % of a step, 1 STEP, or 2 to 128 steps): a long note goes on under the notes after it, a chord's notes can end apart, and REC and TAKE record them so; with REC off a key picks one note of a chord. SHIFT + OCT− / OCT+ copy and paste the selection, SHIFT + EDIT deletes it (on the drum grid copy and paste follow the LANE: a figure moved from lane to lane). SEQ › FEEL, 16 tiles, sets CHANCE (OFF, 1–100 %, then the trig conditions), RATCHET (×1–4, FLAM), NUDGE and TYPE (accent, slide) on every selected step. A new note is 1 STEP long (PATTERN's GATE 100 %); PATTERN's PRESETS turns the direction
• 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. (2.0) Entries on CHAIN play and edit as one long pattern, SONG ONCE plays the lists once and stops, SONG's NEW and COPY+ put a new or a copied pattern in the list in place, and an entry can carry a sound of its own, switched in on the entry's first step (Patterns, lists and the song)
• 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 (2.0: held, a black key cuts its track while it's held); 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 (MENU › CONTROL › RETURN), or stay where they are with OCT+ (2.0)
• 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 come back (OCT+ keeps them), not recorded; (2.0) over a bar, or as MENU › CONTROL › RETURN says (SNAP, 1 BEAT, 1 BAR), the same for FX's macros and PERFORM's throws
• Lane mutes (1.3): on a DRUM or DRUM-X track the EDIT layer's black keys 1–8 mute its lanes; OCT− puts them back as they were when the layer opened, and (2.0.1) OCT+ turns every lane on at once
• DUCK (FX › DUCK): a track dips under another track's hits, the sidechain pump
• Effects: per track DIST, in five types on FX › DRIVE (INSERT's SOFT, HARD, FOLD, CRUSH, FUZZ) 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 the tracks' mutes 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
• One mute (2.0): the black keys F#3 to F#4 are the six tracks' MUTE in the GLO, FX and PERFORM layers alike: a tap mutes or unmutes the track (the MIXER's MUTE, saved; PERFORM's at its LAUNCH point), held the track is cut only while the key is. A muted track is silent at once, its sounding notes too
• 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. (2.0.3) A chord goes whole into the arpeggiator on MONO, LEGATO and UNISON sounds too. KBD HOLD (2.0.3): ARP 2 › HOLD ON with the ARP's MODE OFF holds the notes you play without an arpeggio: let go and they go on sounding; the next key you press with no key down starts a new chord, keys pressed while others are still down join it. HOLD off, the ARP on or another track ends them. QUANTIZE SOLO (2.1, #74): chords on the white keys, a tune on the black ones, single notes of the same scale (see Scale keyboard). Chord follow (2.1): a track set to FOLLOW another plays in that track's chords: a bass or an arp written in C moves to F as the chord track plays F (see Chord follow)
• MOD (2.0: one page, LFO › MOD): KNOB 1 picks the route, 1 to 11. The first seven are fixed, drawn as a grid: the LFO's depths to PITCH, CUT, SHAPE and AMP and the envelope's to PITCH, CUT and SHAPE (1.x's LFO DEST and ENV DEST pages), only their AMOUNT turning; routes 8 to 11 are the modulation matrix
• 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 (1.3; LFO 2's fourth card since 2.0): 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

Patterns, lists and the song

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, each note's own length, 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 (2.0: the first free number after its original's, so copies sit beside it).
• SAVE › PATTERNS shows the pool, what each pattern's LENGTH is and how many entries use it; KNOB 4, ACTION, is what OCT+ does (stopped, after asking): CLEAR a pattern nothing uses, EMPTY one (2.0: its notes and automation go, its number, its settings and the entries naming it stay) or UNUSED (2.0: every pattern nothing uses cleared at once).
• 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).
• SEQ › SONG edits the lists: KNOB 1 the entry, KNOB 2 what goes in it (OCT+ puts it in, the footer saying what): REST, a kept pattern, NEW (2.0: a new empty pattern), COPY (a copy of the entry's pattern), COPY+ (2.0: the copy into the first empty entry after it, this entry left as it is), CLEAR, then (2.0) SOUND (the track's sound now onto the entry: SET SOUND STRINGS) and NO SOUND; KNOB 3 the REPS (CHAIN, 1x–16x); KNOB 4 SONG (OFF, ON, ONCE).
• An entry's sound (2.0): when the track comes onto it, the entry loads its sound, as PRESETS or USER would (a program change): all but the track's own settings (LEVEL, PAN, MUTE, ARP, SCALE, the pattern's, the SLICER, the ducking). Playing, it switches on the entry's first step, with its pattern; stopped, at once. An entry without one leaves the sound as it is, so give the first entry one too to come back to it when the song loops. The sound is the preset or user sound as it was loaded: one edited since is refused (SOUND EDITED: save it on SAVE › USER first). A tile with a sound has its corner cut, and with nothing picked the footer names the entry's sound.
• 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. SONG ONCE (2.0): PLAY starts every track from its first entry, each plays its list once, then goes quiet, and when the last one ends the transport stops.
• A chain (2.0): KNOB 3 below 1x is CHAIN, the entry going on into the next. Entries on CHAIN with the one they end on are one pattern wherever the track plays them, each part with its own LENGTH, DIV and SWING: the header names the chain and the part (A-B · 02), NOTES counts the steps on through the parts (NOTES 71), and a note can go on from one part into the next (LENGTH, REC and TAKE across them). With SONG OFF a track loops the whole chain; with SONG ON or ONCE it plays the chain through, its last entry's REPS repeating all of it. A launch onto any part starts it from its first. An empty entry ends a chain.
• 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.

Controls

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 the selected track the moment it is pressed; on an armed track it disarms every track (its light is on while any track is armed). 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 NOTES 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 NOTES and FEEL it moves the step cursor, on PATTERN it turns the direction, on lists it picks. With SAVE › PRESETS' LIST on a type (BASS, PAD ..) it steps through that type only
• On NOTES and FEEL, SHIFT + PRESETS stretches the selection over a range of steps, SHIFT + OCT− / OCT+ copy and paste it, SHIFT + EDIT deletes it; with REC off a key picks its note in the selection
• On action pages and in dialogs, OCT+ does it and OCT− goes back
• Hold a step on SEQ › NOTES (on the drum grid its white key; on the piano roll the step you are entering, REC armed and stopped) and turn KNOB 1–4 to lock those parameters on that step: the four of the sound page you were on last (HOME's after HOME)
• Save a sound: stop, tap SAVE (USER), pick a slot with KNOB 1, OCT+, name it with the keys, OCT+

The FX layer's keys

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; a key still held as the layer locks stays on, latched). 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 are tracks 1–6's mutes, as on GLO and PERFORM: a tap mutes or unmutes the track, held it is cut until you let go. 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). Let go of FX and they come back over a bar (MENU › CONTROL › RETURN: SNAP, 1 BEAT or 1 BAR, as MOMENTARY's values and PERFORM's throws), or once you let go of the effect keys you are still holding; OCT+ with FX held keeps them.

Engines

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); (2.0) EDIT › LANE MIX, on DRUM and DRUM-X, its level and PAN (KNOB 1 the lane, or a key struck): a lane panned as the track's PAN pans, the track's PAN over the whole kit, DRIVE, the INSERT and the sends hearing the kit as before. (2.0) KIT USR1–USR3 plays a user sample slot as the kit: each lane its sample on its key (KICK C2, SNARE D2, CLAP D#2, CL HAT F#2, OP HAT A#2, TOM A2, RIM C#2, BELL G#3), with the lanes' level, tune, decay and pan, the open hat cut by the closed one; a lane with no sample is silent. The editor's Samples tab builds such a slot (Drum kit: a WAV a lane)
• 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.

Menu

Hold HOME and let it go for the menu. It is in five tabs: DISPLAY (THEME, PLAYHEAD, LARGE, ANIM, LEDS, SCREEN OFF, HINTS), CONTROL (HOLD, KNOB ACCEL, BPM LOCK, SCALE LEDS, STEP PREVIEW, RETURN), AUDIO (SPEAKER EQ, USB LEVEL, CLICK, CLICK LEVEL, COUNT-IN, TUNE), SYSTEM (RESTORE LAST, CPU, CPU CLOCK, HARDWARE CALIBRATION, RESET SETTINGS, ABOUT) and MIDI (CLOCK, MIDI IN, MIDI LEARN, LEARN CLEAR, T1–T6 CHANNEL); a tab of more than six rows scrolls. 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.

Scale keyboard

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).

QNT SOLO (2.1, #74) plays chords on the white keys and a tune on the black ones. The white keys play as with WHITE, CHRD's chords too. The black keys walk the same scale one note at a time, five to an octave: C#4 plays ROOT, F#3, G#3 and A#3 the three scale notes below it, and the run goes up to F#5, seven scale notes above (on the SMK-37, C#3, D#3, G#5 and A#5 carry it on). A black key never plays a chord, in live recording and step entry too; KBD HOLD doesn't hold it, and pressing one leaves the held chord sounding (the SMK-37's sustain pedal still holds every key); with the ARP on it sounds directly, and is recorded so, while the white keys' chords go into the arpeggio. SCALE LEDS light the black keys too. A Skiff before 2.1 opens a SOLO track as SEQ+T: every key snapped to the scale.

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.

Chord follow

Press SEL a third time for the FOLLOW page (2.1). Write a bass line or an arp once, in the track's own key (its ROOT), and let another track's chords move it. Only the following track is set; the chord track needs nothing.

• FOLLOW (KNOB 1): OFF, or the track whose chords this one follows (T1..T6; never itself).
• MODE (KNOB 2): KEY moves every note by the distance from this track's ROOT to the chord's note, the nearest way (up to six semitones up, five down): C E G under an F chord plays F A C. SCALE moves the notes along this track's own SCALE by as many scale steps, so they stay in key: C E G in C major under Am plays A C E. FIT moves each note to the nearest note of the chord itself (a tie goes down), for arps and pads over any chord.
• NOTE (KNOB 3, for KEY and SCALE): which note of the chord counts: its ROOT (worked out from its notes, inversions too: F for A C F), its lowest (LOW: A for A C F), its highest (HIGH) or the one started last (LAST).

The chord is the notes of the chord track's latest step (as they sound), or the keys and MIDI notes it holds: a key pressed with none held starts a new chord, the ones pressed while it is held join it (an arpeggio's held chord, not each of its notes; QUANTIZE SOLO's black keys are a tune, not the chord). It stays until the next one, and a muted chord track still leads. Every note the following track sounds moves as it starts: its steps, its keys, MIDI IN and its ARP. A note already sounding, or tied on, keeps its pitch; on a step where the chord changes, the chord comes first. What you record or enter is what you played, so a take plays back as you heard it and moves again with the chords. STOP clears the chords: the following tracks play as written until their chord track plays again. Drum kits neither follow nor lead. MIDI OUT sends the keys as pressed. The page shows the chord, the note it goes by and what the track does with it ("T2 KEY +5"). A Skiff before 2.1 ignores FOLLOW: the tracks play as written.

Build from source

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.

If the FM-1 does not start

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-2.1.1.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.

Support

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

Credits

• 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)

Licence

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)