Custom firmware for the M-VAVE FM-1: FM drums you program on the device, and a DX7 on top (six operators, 32 algorithms, real voice editing).
Free and open source (GPL-3.0). A fork of SLOOP, which is based on Felucca. Not affiliated with either.

Install from the browser · Manual · Cheat Sheet (2 × A4) · Web editor · Releases · Report a bug

sloopDX 2.5 in a minute: FM with cutoff and resonance, the sounds, drums you program, 128 steps, OMNI.

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sloopDX turns the FM-1 into what it says on the box: an FM synthesizer. There is one engine, a six-operator DX7 voice (Dexed's msfa core, ported to integer C and checked against Dexed (99 % of samples identical, the rest within 1-2 LSB)). The drum track plays FM drums made with the same engine. SLOOP's live workflow stays as it is: tracks, layers, sequencer, song mode and effects — and, from SLOOP 2.3, USB audio, a MIDI keyboard on the jack, MIDI clock, lights for playing in the dark and a full backup. The sample engines, sample sets and the other eight engines are gone.

New in 4.0: both processor cores, and SLOOP 2.6 / 2.7's MIDI. The sound is computed on both of the FM-1's cores (about twice the room for DX7 voices and effects), every track has its own MIDI channel, sustain pedal, pitch bend, MIDI LEARN, step entry from a keyboard, the punch-in effects and the buttons over MIDI, MIDI clock out; 15 arp modes and KBD HOLD; 27 punch-in effects; an INSERT effect on every track (From SLOOP 2.6 / 2.7). New in 3.5: a DAW picks the sounds. MIDI Program Change loads a preset into the track the channel plays, as the PRESETS knob does (MIDI). New in 2.2: patterns up to 128 steps. The four tracks share 256 steps: one track can run 128, the others take what is left; OCT− / OCT+ page through 8 pages. New in 2.1: a drum machine you can program. Every one of the 16 drum sounds has eight macros on the FM-1 (TUNE, DECAY, SWEEP, BRIGHT, NOISE, LEVEL, PAN, CHOKE, plus its own reverb send). A real noise operator gives snares, claps and hats their hiss. Steps can lock TUNE and DECAY per hit. MY KIT keeps your own kit in flash and travels as a .syx, and the dice rolls a whole new kit from a seed you can roll again.

Status: 4.0, a beta. It builds and every host test passes; 3.5 is installed and played on a real FM-1, 4.0 (the second core, SLOOP 2.6 / 2.7) has not been on a device yet. Still open: 4.0 on the device (ABOUT must say 2 CORES), a full check of the web editor against the device. Install at your own risk, and please report what you find. See Status.

Why sloopDX

I bought the FM-1 for one reason: a DX7 sound, a real FM synth, in a little box. Out of the box it is exactly that. Then two projects took it further. Baud Girl's FM-1+VA turned the sequencer into something much better and lets you program the FM sound on the device, with a list for every parameter. SLOOP turned it into a groovebox you play live, with a sequencer, layers, song mode and effects that are a joy to use, but without the FM sound. I wanted the FM back.

sloopDX is my approach to combine both: SLOOP's live workflow, with a DX7 inside. The engine is Dexed's DX7 core, ported to the FM-1's chip and checked against Dexed sample by sample, so a DX7 patch sounds as it should. The voice editing follows the idea of Baud Girl's list (its concept, rebuilt here; Baud Girl's firmware is closed source) in the DX7's own names. Your banks load as they are, 256 voices of them, and the drums are FM too.

Contents

1. Why sloopDX
2. From SLOOP 2.6 / 2.7 (new in 4.0)
3. From SLOOP 2.5 (3.4)
4. From SLOOP 2.4 (3.3)
5. From SLOOP 2.3
6. Screens
7. What it does
8. Status
9. Install
10. Your first beat in 60 seconds
11. The controls
12. The menu: settings of the FM-1
13. MIDI and USB audio
14. The web editor
15. Compatibility
16. Troubleshooting
17. Specifications
18. Documentation
19. Building and tests
20. Contributing
21. Credits and thanks
22. Licence

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From SLOOP 2.6 / 2.7 (new in 4.0)

sloopDX 4.0 takes from SLOOP 2.6 and 2.7 what fits next to its DX7 and its drums: above all the second core and the MIDI. None of it has been tried on a device in sloopDX yet.

Two cores	The sound is computed on both of the FM-1's processor cores (andrerezemini, SLOOP #111, on the dual-core start of Charles Vestal's X0X and keremimo's Melodee): the last synth part and the drums on the second core, the rest on the first, the same sound bit for bit. HOME menu → SYSTEM → 2ND CORE OFF goes back to one core; ABOUT says 2 CORES. At power-on the two supplies are raised to M-VAVE's own levels (after X0X 1.0.9). On the way the RAM went from 94 to 76 KB of 96: room again.
Each track on its own MIDI channel	GLO → MIDI: CH1, CH2, CH3, CH4 (the drums), OFF or 1–16, in and out; GLO → MIDI 2: IN (NOTES, CLOCK, or one channel only: CH 1–16), OTHER (the channels no track has: the selected track, or nothing), OUT (KEYS / SEQ), BEND. Settings of the FM-1, kept through power-off and in the backup.
Sustain, pitch bend, Program Change	CC 64 holds the notes you let go (recorded as heard); the wheel bends the track by up to BEND semitones (1–12); Program Change loads a sound, on the drum channel kit n.
MIDI LEARN	GLO + F#3, turn a knob of the FM-1, move a knob of your controller — done. Up to 16 CCs, kept through power-off; HOME menu → SYSTEM → MIDI LEARN CLEAR forgets them.
Step entry from a MIDI keyboard	On the STEP page your keyboard writes the cursor's step as the FM-1's keys do (a chord: the notes held together).
GLO → MIDI 3	FX CH: the 27 punch-in effects from a controller (notes F3 … G5); DR MAP 1-16: the 16 drum sounds from any 16 notes in a row; REMOTE: the 14 buttons from CC 102 … 115; CLOCK OUT: the FM-1 as the clock master on USB.
Arp	15 modes: REPEAT, DNUP, UP+8, CONV, DIVG, PINKY, THUMB, WALK and CHORD after sloopDX's OMNI and FLW; ORD plays the notes in the order pressed. KBD HOLD: ARP 2 → HOLD ON with the arp OFF holds the notes you play (a pad, a drone). A sound loaded keeps the arp running; ARP SWG works with the sequencer stopped; a latched arp follows TRN, ROOT, SCALE and KEYS (#191).
Recording	Overdub over held notes: a note recorded under a pad tied over the bar no longer cuts it. SEQ + a synth step + KNOB 2: its velocity (1–127).
27 punch-in effects	Hold FX: the black keys are eleven more — KILL LOW / MID / HIGH, REWIND, OCT UP, FLANGER, AUTO-PAN, FREEZE, LOOP 8T, MONO, FADE OUT. REV / ECHO THROW: FX + OCT− / OCT+, every send full while held.
INSERT, LFO 2, ENV SYNC	FX → INSERT on every track (the drum track too): SOFT, HARD, FOLD, FUZZ, CRUSH, PHASR, FLANG, CHOR with a dry / wet MIX, next to sloopDX's DIST page. LFO → LFO 2: the LFO synced to the tempo, TRIG, POL. ENV DEST → ESYNC: ATK, DEC, REL as note values.
TEXTURE	GLO → TEXTURE: a looping bed under the mix — VINYL, TAPE, RAIN, WIND, RADIO, ROOM — with level, tone, a slow breath over 1–16 bars, with the transport or always, pumped by the kick if you like. Kept with the project and each section.
Live drum mutes	EDIT + a black key on the drum track: the white keys mute and unmute their sounds in the sequencer (nothing erased); the mode stays until a black key again.
The menu, in sections	SCREEN, LIGHTS, AUDIO, SYSTEM; SELECT goes to the section, KNOB 1–4 set its rows. New: KNOB ACCEL (a fast turn sweeps wider), USB RATE (AUTO, 44.1, 48 kHz), 2ND CORE, MIDI LEARN CLEAR. FACTORY RESET is on the ABOUT page now (OCT+ twice).
Smaller things	Favourite sounds (PRESETS page, KNOB 4: right adds, left removes; up to 16 at the top of the list); SAVE → SECTION A–D with KNOB 2 ERASE; LEVEL and PAN glide instead of stepping (after JIANT FM); SELECT walks a family's pages and counts them; a look-ahead master limiter and no clicks when a sound is loaded over sounding notes; the delay's TIME gets 1/4D; Terminus Bold on the screen.

Not taken: SLOOP's REC QUANT off (it needs SLOOP's per-step nudges, which sloopDX does not have yet), the drums' SOUND page (sloopDX's lanes have TUNE and DECAY and six more), looping user samples (no sample engine here). The web editor's LIVE page, songs as files and the Theme page are planned for sloopDX's editor; the firmware already answers the LIVE page's command. Projects of 3.x load as they are (format 7 → 8); a project saved in 4.0 does not open in 3.x.

From SLOOP 2.5 (3.4)

sloopDX 3.4 takes from SLOOP 2.5 what fits next to its DX7 and its drums. None of it has been tried on a device in sloopDX yet.

MIDI CCs	A controller's knobs now set the sound, on the track the channel plays (as the notes): CC 74 CUT and 71 RESO (the low-pass behind the DX7 voice), 73 / 75 / 72 the ATK / DEC / REL macros, 7 level, 10 pan, 5 glide, 91 / 93 / 94 the reverb, chorus and delay sends. On the drum channel: 7, 91 and 94 set GLO → DRUMS LVL, REV and DLY, 10 the pan. With IN = CLOCK they are ignored, as the notes are.
A delay send for the drums	GLO → DRUMS → DLY (next to REV) sends the drum bus into the tempo delay: echoing hats, dub snares. Kept in the project; older projects load with 0.
USB audio at 48 kHz too	Phones, tablets and apps that only take 48 kHz can now record the FM-1: it resamples in the FM-1 when the host asks for 48 kHz (after Felucca 1.1.5). At 44.1 kHz nothing changed.
Swing reads 0 to 100	0 straight, 100 the most (it read 50–75 %). The swing itself and your projects did not change.
SEL	The key / scale button between FX and ENV is called SEL everywhere, as printed on it (it was written SCL).
DUST off at power-on	The master's hiss and crackle (GLO → MASTER DUST, FX + KNOB 2) start at 0 every time the FM-1 is switched on or updated; a project you load keeps its DUST.
Fixes	In chord mode a key on the STEP page writes the whole chord it plays, not only its root; the click (and the REC count-in) is heard with the drum track muted or another track soloed; the DRUMS page's level dial goes from ghost on the left to hard on the right.

Not taken: SLOOP's PHYS and NOISE engines and their sounds, its drum synth (SYN kits; sloopDX has its own FM drums and MY KIT), the cartridge import into its FM6 bank. The editor's piano roll, MIDI file export / import and Song page are planned for sloopDX's own editor.

From SLOOP 2.4 (3.3)

sloopDX 3.3 took from SLOOP 2.4 the fixes and the small additions that fit next to its DX7 and its drums. None of it has been tried on a device in sloopDX yet.

Sequencer to MIDI OUT	GLO → SYSTEM → MIDI = SEQ: the steps, the arp, the rolls and the OMNI chords go out on USB MIDI, each track on its keys' channel (drums on 10). Drive another synth, or record the notes in a DAW. KEYS (the default): only what you play.
Clock only	GLO → SYSTEM → IN = CLOCK: follow a DAW's clock and ignore its notes.
Longer steps, dotted delays	DIV goes to 1/2, 1BAR and 2BAR; the delay's TIME has 1/8D and 1/16D.
Quick chain	Hold SAVE and tap A B B C…: let go and the sections play in turn, each for its pattern's length, looped. One section tapped alone stops it.
USB SERIAL	HOME menu → USB SERIAL, OFF by default: without the serial console, macOS 13–15 show the USB audio input again. ON (at the next start) for developers.
Fixes	A MIDI START during the REC count-in records at once; swing leaves triplets and whole-beat steps alone; DIV or RATE turned right after PLAY no longer skips a step; a knob still turning as you let go of a layer no longer changes the page; the editor never writes flash while the song plays (stop it first); NOTES lights short sequencer notes too; 12 kHz and −12 dB read in full; a divide by zero can no longer stop the FM-1.

Not taken (yet): parameter locks, micro timing and fills (they need room the project and the drum locks already use), the per-track filter, CHORD+, the visualiser, SLOOP's FM6 engine (sloopDX has its own DX7) and its new editor.

From SLOOP 2.3

sloopDX carries everything SLOOP 2.3 added to the FM-1 itself. None of it has been tried on a device in sloopDX yet.

USB audio	On USB the FM-1 is also an audio input (Felucca, 44.1 or 48 kHz stereo, no driver): record it in your DAW or Audacity over the same cable. Its level follows the MASTER knob, or stays at a fixed full level (HOME menu → USB AUDIO). From Felucca 1.0.
MIDI keyboard on the jack	The 3.5 mm TRS MIDI IN works: a keyboard or a pad controller through a TRS-to-DIN adapter. Channels 1–3 the synths, 10 the drums, 4–16 the selected track. No note left hanging.
MIDI clock in	GLO → SYSTEM → SYNC = USB or TRS: sloopDX follows a DAW or a drum machine — tempo, START, CONTINUE, STOP — pulse by pulse, with no drift.
Record your way	The REC screen has three dials: mode (free: the tempo follows your playing, or tempo: the tempo you set), length (1, 2 or 4 bars), start (your first note, or a one-bar count-in after PLAY).
Lights for playing in the dark	HOME menu: LIGHTS (every button glows, LOW / MID / HIGH), KEYS (the C keys or every white key), NOTES (the notes playing light their keys, by @renebohne).
Backup and restore	The web editor saves everything on the FM-1 in one file — the music in progress, projects, user presets, settings and, on sloopDX, your DX7 bank — and puts it all back.
Steadier	Knobs that answer every click; no dropped notes over USB MIDI; one voice fades on overload, never the bass or the lead; keys a millisecond faster; no stuck note after a VOICE change; stricter checks of what is read back from flash.

Screens

_{Start-up with the 32 algorithms, the tracks, the FM drum grid, the DX7 voice list, an algorithm, an operator, the step layer, about. (Host renders of the firmware's own drawing code.)}

What it does

• Programmable FM drums (2.1): on the kit page, tap EDIT for the sound you last played: KNOB 1–4 are TUNE, DECAY, SWEEP and BRIGHT; PRESETS turns to NOISE, LEVEL, PAN and CHOKE, then the lane's REVERB send. Your edits are saved with the project. Hold SEQ and a step: KNOB 4 locks TUNE and PRESETS locks DECAY for that hit only (a ★ on the step).
• MY KIT and the dice (2.1): SAVE twice on the kit page bakes the kit with your edits into MY KIT (kit 5, kept in flash). On the lane page's third page, KNOB 3 rolls a dice kit from rules per sound and KNOB 4 rolls only the sound you edit (turn once, then again to confirm); the kit's seed shows in the corner, and the editor rolls a given seed again. The web editor loads and downloads MY KIT as a .syx (voices 1–16 the drums, 17–32 their table).
• A noise operator (2.1): drum operators can play noise instead of a sine (sample and hold of a 32-bit generator; the operator's frequency is the colour). The factory kits use it for snares, claps, hats, cymbals and shakers. Synth voices never do: they stay bit for bit as Dexed plays them.
• OMNI, the chord harp (2.5): set a synth track's ARP MODE to OMNI and the keys become an Omnichord: the 11 black keys are chord buttons (F C G · Dm Am · Em G7 E7 · D7 Bb · A7; TRN transposes them), the 16 white keys are strings over the chord's tones, so a swipe is a harp glissando and nothing sounds wrong. Recorded, the chords go into the pattern and set the chord again on playback. ARP MODE FLW on another track makes its pattern follow the chord's root: a bass that walks with your chords. See OMNI.
• One page per effect (2.7, 3.0): tap FX for SENDS (the four sends as dials in a row), then DIST (drive, tone, type SOFT / HARD / FUZZ / CRUSH, mix), CHORUS (send, rate, depth, mix), DELAY (send, time, feedback, mix) and REVERB (send, size, damp, pre-delay). See The effect pages.
• DX7 engine: 6 operators, 32 algorithms, operator envelopes with rate and level scaling, pitch envelope, LFO with pitch and amp modulation, feedback. The same output as Dexed for the same patch.
• 20 factory voices in the DX7 tradition (designed here, not copied): EPIANO 1 and 2, FM BASS, SLAP BASS, SUB BASS, BRASS, STRINGS, GLASS PAD, BELLS, MARIMBA, ORGAN, CLAV, PLUCK, FLUTE, SAW LEAD, KOTO, three modern basses (DEEP SUB: a pure sine an octave down; 808 SUB: it drops into the note and dies away; REESE: two detuned saw stacks over a sine sub) and INIT VOICE.
• Your own DX7 banks: 8 banks of 32 voices (256) in flash, standard bulk dumps (.syx, 4104 bytes), loaded from the web editor's Library tab or with tools/fm1_bank_upload.py --bank N. The bank in use plays as 21–52 (U01–U32), and PRESETS runs on into it. The checksum is verified and every value is clamped to its range.
• Voice edit like a DX7: every parameter of the voice on the FM-1 itself, as a list (in the style of Baud Girl's FM-1+VA): algorithm with a drawing of the operators, feedback, each operator's level, ratio, detune, envelope, velocity and key scaling, the pitch envelope, the LFO, the name. Operators can be switched off to hear the rest, or soloed to hear one alone; the algorithm drawing shows each operator's level, and how loud it is while a note sounds. SAVE stores your bank. The web editor's Voice tab has the same, on one page with sliders, and imports / exports single voices (.syx).
• Quick knobs per voice: BRITE (modulator levels), ATK, DEC and REL (the operator rates), FDBK.
• A low-pass behind each voice: CUT and RESO, on KNOB 1 and 2 in the voice list (the value shows while you turn; two small dials top right show at a glance whether the filter is set), moved by ENV / LFO → FLT. At CUT 127 it is out of the way: the voice sounds exactly as the DX7 patch.
• Three synth parts plus a drum track, sharing an 8-voice budget. Each part plays the whole keyboard (no split), and each track has its own pattern length.
• FM drums: 16 lanes on the white keys (kick, kick 2, snare, clap, closed / open / pedal hat, rim, tight snare, low / high tom, crash, ride, shaker, conga, cowbell). Four kits:
  • DX KIT, the factory kit
  • 808 FM, an analogue drum machine in FM: round kicks, metallic hats
  • ELECTRO, short and clicky
  • METAL, inharmonic and industrial: anvils, bells, a gong
  • MY KIT, yours: saved from any kit with your edits, loaded as a .syx, or rolled with the dice
• Drum details: a pitch sweep on kicks and toms, a real multi-hit clap, and hat choke. The bus: each sound's level and pan, then DRIVE and COMP on the kit page (a soft clip; a compressor with make-up gain), then each sound's reverb send.
• From SLOOP: the layers (FX punch-in, edit, arp, steps, scale and chords, mix, song), free takes, swing, chorus / delay / reverb sends, DUST and DUCK, undo / redo, projects and user presets.
• Recording your way: record at once while playing, or arm and choose on the REC screen — a free take or the tempo set, 1, 2 or 4 bars, from the first note or after a one-bar count-in.
• MIDI: USB MIDI in and out, class compliant; the TRS MIDI IN jack for a keyboard or pads; MIDI clock in (USB or TRS). Details: MIDI and USB audio.
• USB audio: the FM-1 is also a USB audio input — the master output, 44.1 or 48 kHz stereo, no driver, on the same cable as MIDI and the editor.
• Lights: every button can glow so its label is readable on a black FM-1; the C keys or every white key can glow too; the notes playing can light their keys. See The menu.
• Memory and safety: autosave (stop and leave it 2.5 s; at power-on sloopDX comes back as you left it), 4 projects, 32 user presets, undo / redo, a full backup and restore from the web editor, and safe updates (the installer checks the package by SHA-256, the update loader by CRC; an interrupted install finishes when you press Install again; USB rescue with OCT− at power-on).

Status

3.5, a usable beta. What is known:

• Works: the firmware builds with the JieLi toolchain (RAM about 85 KB of the 96 KB budget) and the host test suite passes: audio renders against golden hashes, the voices, the sequencer (REC modes, count-in, MIDI clock), the UI pages and layers, the DX7 voice list, flash storage, the 8 banks, the update loader, the .syx import, the bank upload, MIDI and USB audio, and the web pages. On the FM-1: install, the boot screen, the DX7 voice list, a ROM bank in flash, the drum kits and the levels have been played.
• From 1.9: projects, user presets and the editor's library keep their sounds. Three factory voices came in before INIT VOICE, so the bank moved from 18–49 to 21–52; older saves are renumbered when they load, and the new CUT starts open.
• From 2.0: projects load with every drum sound as its kit (no macros, no locks); the project format is now 5. MY KIT starts as a copy of DX KIT.
• Bank voices were too quiet (fixed in 2.2): PRESETS loaded a bank voice (21–52) with its filter shut, and a −6 dB trim on top. Now the filter is open and the bank voices sit at the factory voices' level (measured on the eight DX7 ROM banks). Projects and presets saved with the shut filter open it when they load.
• From 2.1: projects load as they were (each track's 64 steps); the project format is now 6. Only the steps inside a track's LENGTH are saved now, so steps beyond it are gone after a save.
• From 2.4: projects and presets load as they were. ARP MODE has two new values (OMNI, FLW): set them back to OFF before you go back to an older sloopDX, which does not know them.
• Still to check on the device: the web editor end to end (live sync, the Voice tab, the bank selector), the CPU with three synth tracks and the drums all sounding, and SLOOP 2.3's USB audio, MIDI IN jack and lights.
• Sound: the 20 factory voices are designed here (no Yamaha data); they want a pass by ear. For the classic sounds, load the original DX7 ROM banks (yamahablackboxes.com) into one of the 8 bank slots.

The DX7 core matches Dexed: 99 % of samples identical, the rest within 1–2 LSB (tests/dx7ref/). The full list of open items is in TODO.md.

Install

From the browser

1. Open the sloopDX installer (the docs/ page of this repository) in Chrome or Edge on a computer.
2. Connect the FM-1 by USB — a data cable, directly (no hub).
3. Press INSTALL, allow MIDI access, and wait for Done. The FM-1 restarts on the sloopDX logo.

Nothing to download or compile. Your projects, user presets and settings are kept. After an install, unplug and plug the FM-1 back in once so the computer finds its USB audio input.

Other ways

• Python: the .fwsc of a release (or docs/firmware/sloopdx-3.5.fwsc) with python tools/fm1_install.py sloopdx-3.5.fwsc (needs pip install mido python-rtmidi).
• Build it yourself: see Building and tests; on Windows, INSTALL-SLOOPDX.bat builds sloopDX and opens the installer locally.

Going back

• To SLOOP: install the .fwsc of a SLOOP release. Save a backup first: projects and presets made on sloopDX name DX7 voices and FM kits that SLOOP does not have, so expect to pick sounds again.
• To the official firmware: save a backup with the editor first, then use M-VAVE's own updater, M-UPGRADE, with the FM-1 V15 firmware from m-vave.com (close every other app that uses MIDI). The installer page's Return to the official firmware (V15) does the same from the browser: select M-VAVE's unmodified FM-1.fwsc and install it. To come back, install sloopDX again and restore your backup.

Rescue

• The FM-1 no longer starts sloopDX: hold OCT− alone while switching it on (USB RESCUE), then install again.
• An install was cut off: the FM-1 stays in update mode; press INSTALL again and it finishes.
• If an FM-1 no longer starts at all, recovery needs FM-1-transporter.

Custom firmware is installed at your own risk. No warranty.

Your first beat in 60 seconds

1. ALGORITHM to track 4 (beige, drums). The white keys are 16 FM drums; PRESETS picks a kit (try 808 FM or METAL).
2. Press REC and play a beat freely, at your own tempo. Hold OCT− while you hit for ghost notes, OCT+ for hard ones.
3. Press REC on the "1" after your last bar. The loop closes, its length sets the tempo, the hits snap to the grid and it plays at once. (Prefer a set tempo, or a count-in? Turn KNOB 1 and KNOB 3 on the REC screen before you start.)
4. REC again while it plays: you record on top. Hold ARP and hold the hat key for a hat roll.
5. ALGORITHM to track 1 (FM BASS), REC, play a bass line. Hold SEL and press the key of your song; on track 2 (EPIANO 1), hold SEL and turn KNOB 1 to 7TH: every white key now plays a chord.
6. Hold FX and press a white key for a punch-in effect; still holding FX, turn KNOB 2 for DUST, KNOB 3 for DUCK.
7. Tap EDIT on a synth track: the DX7 voice list. SELECT to OP2, tap EDIT, turn ALGORITHM on Output Level: the tone opens up. PRESETS jumps to the next operator, HOME goes back, SAVE stores. On the EDIT pages (More Pages), KNOB 2 BRITE does the same in one turn. In the voice list, KNOB 1 CUT and KNOB 2 RESO are the low-pass.
8. A mistake? Hold EDIT and press OCT−: undo.

The controls

Control	What it does
MASTER	volume (and the USB audio level, if USB AUDIO is on MASTER)
SELECT	tempo, on every page, even inside a layer
ALGORITHM	the selected track: 1 · 2 · 3 (synths) · 4 (drums)
PRESETS	the selected track's voice, or the drum kit
KNOB 1–4	what the four dials at the bottom of the screen show, each in its colour
OCT− / OCT+	octave (both: back to 0) · on the drum track, held: ghost / hard hits
FX · SEL · ENV · LFO · EDIT · GLO (top row)	tap: their pages (EDIT on a synth track: the DX7 VOICE and SHAPE pages) · hold FX, SEL, EDIT, GLO: a layer. SEL is the second button of the top row, between FX and ENV
HOME	the TRACKS screen · hold: the menu · tapped while a layer is held: lock it
SAVE	on TRACKS: the SONG screen · elsewhere: the SAVE pages · hold: the song layer
ARP · SEQ	tap: their pages · hold: note repeat · steps
PLAY	start / stop all four tracks; its light flashes on every beat
REC	playing: record now / stop · stopped: arm (the REC screen) · hold: clear the track
EDIT + OCT− / OCT+	undo / redo

Colours, from the DX7's panel: cyan track 1 and KNOB 1, light blue 2, pink 3, beige 4 (drums). White is what you touch; red is recording.

The menu: settings of the FM-1

Hold HOME. The menu has four sections: SELECT goes to the one before / after, KNOB 1–4 set its rows (the knob's colour marks its row), PRESETS moves the cursor, OCT+ steps the cursor's row round or opens it, OCT− closes. These are settings of the FM-1, not of a project: loading a project or NEW does not change them, and the backup keeps them.

Section	Item	Choices	What it does
SCREEN	COLOR	6 palettes (DX the default), your theme	the screen's colours
	ZOOM	OFF / ON	a large readout of the value you turn
	KNOB ACCEL	ON / OFF	4.0: a fast turn sweeps wider, a slow one is one value a detent
LIGHTS	LIGHTS	OFF / LOW / MID / HIGH	every button glows at that level; what is active stays at full light
	KEYS	OFF / C KEYS / WHITE KEYS	the C keys, or every white key, glow too
	NOTES	OFF / ON	the notes playing on a synth track light their keys, on every page and in every layer
AUDIO	SPEAKER LOWCUT	OFF / ON	a low cut for the small built-in speaker
	USB AUDIO	MASTER / FULL	the level of the USB audio input: follows the MASTER knob, or a fixed full level
	USB SERIAL	OFF / ON	the serial console on USB (for developers), taken at the next start (RESTART shows until then). OFF, the default: macOS 13–15 show the USB audio input (3.3)
	USB RATE	AUTO / 44.1 / 48 KHZ	4.0: the rates the USB audio input offers, at the next start (for phones that record it distorted)
SYSTEM	2ND CORE	ON / OFF	4.0: the sound on both processor cores; OFF: one core (ON again: at the next power-on)
	HARDWARE CALIBRATION		the panel table, if a key or a knob answers wrongly
	MIDI LEARN CLEAR	OCT+	4.0: forgets every learned CC
	ABOUT		the version (sloopDX 4.0), its build date, 2 CORES or 1 CORE, the credits. FACTORY RESET here: OCT+ twice erases everything on the FM-1 (the projects, the working project, the user presets, the 8 DX7 banks, MY KIT and the settings), then restarts as freshly installed. Stopped only; save a backup first (editor → Projects) if you want any of it back

More settings of the FM-1 live elsewhere: GLO → MIDI, MIDI 2, MIDI 3 and SYNC (see MIDI and USB audio) and the REC screen's mode and start.

MIDI and USB audio

MIDI in

sloopDX takes MIDI from two places at once:

• The MIDI IN jack (3.5 mm TRS): a keyboard or a pad controller with a MIDI output, through a TRS-to-DIN MIDI adapter. If nothing plays, try the other adapter type (A / B).
• USB, from a computer or a phone (a DAW, a MIDI routing app) or a USB MIDI host box.

MIDI channel	Plays
1, 2, 3	synth tracks 1, 2, 3 (4.0: GLO → MIDI → CH1, CH2, CH3 set any channel for each, or OFF)
10	the drum track (the nearest of its 16 sounds; GLO → MIDI → CH4 changes the channel; MIDI 3 → DR MAP 1-16: 16 notes in a row)
the others	the selected track: set your keyboard to channel 4 and it follows ALGORITHM (4.0: GLO → MIDI 2 → OTHER = OFF ignores them)

Your own channels (4.0). For an external sequencer with its own channels: GLO → MIDI sets each track's channel (two tracks never share one), GLO → MIDI 2 the rest: IN (NOTES; CLOCK: the clock only; CH 1–16: that channel only, on the selected track), OTHER, OUT, BEND. Sustain (CC 64) holds the notes you let go; the pitch wheel bends by up to BEND semitones. MIDI LEARN: GLO + F#3, turn a knob of the FM-1, move one of your controller (up to 16; SYSTEM → MIDI LEARN CLEAR). On the STEP page a MIDI keyboard writes steps. GLO → MIDI 3: FX CH (the punch-in effects from notes F3 … G5 on that channel), DR MAP, REMOTE (CC 102 … 115 press the 14 buttons: FX SEL ENV LFO EDIT GLO HOME SAVE ARP SEQ PLAY REC OCT− OCT+), CLOCK OUT.

Knobs (CCs, 3.4) set the track the channel plays: 74 CUT, 71 RESO, 73 / 75 / 72 the ATK / DEC / REL macros, 7 level, 10 pan, 5 glide, 91 / 93 / 94 the reverb, chorus and delay sends; on the drum channel 7, 91, 94 are GLO → DRUMS LVL, REV, DLY and 10 the pan. Other CCs are ignored. Program Change (3.5) loads a preset into the track the channel plays, as the PRESETS knob: program 0 is 01 EPIANO 1, 0–19 the factory presets, 20–51 the voices of the DX7 bank in use, then your user presets (the favourites are not counted); on the drum channel (4.0) program n is kit n.

A USB keyboard plugged straight into the FM-1 cannot work: both are USB devices, and a USB link needs a host (a computer, a phone, or a USB MIDI host box). Bluetooth MIDI is not supported: sloopDX, like Felucca, never switches the radio on.

MIDI out

The keys always go out on USB MIDI, each track on its channel (1–3, drums on 10; 4.0: GLO → MIDI). With GLO → MIDI 2 (or SYSTEM) → OUT = SEQ (3.3) the sequencer goes out too: the steps, the arp, the rolls, the OMNI chords and FLW, so another synth plays along or a DAW records the notes. Notes that come in are never sent back (no MIDI loop). STOP, or MIDI back to KEYS, ends every note it sent. GLO → SYSTEM → IN = CLOCK ignores the notes that come in and keeps the clock.

MIDI clock in

GLO → SYSTEM → SYNC = USB or TRS (INT: sloopDX's own tempo). START plays from the top, CONTINUE carries on, STOP stops; the tempo follows the master and the steps follow its 24 pulses a beat, so sloopDX never drifts. When the clock stops for half a second, PLAY on the FM-1 plays at its own tempo again. Clock out (4.0): GLO → MIDI 3 → CLOCK = OUT sends the clock and START / STOP on USB while SYNC is INT: the FM-1 is the master.

USB audio: record the FM-1 on a computer

On USB the FM-1 is also an audio input named "Felucca": 44.1 kHz (or 48 kHz, when the host asks; 3.4), 16-bit stereo, class compliant — no driver on Windows, macOS or Linux. Choose it in your DAW or in Audacity and record: you get the master output, exactly what the headphones play (after DUST, DUCK and FILT). MIDI, the web editor and the installer keep working on the same cable.

• The level: HOME menu → USB AUDIO. MASTER (default): the recording follows the MASTER knob, as the headphones do — keep MASTER well up while you record. FULL: a fixed level, as with MASTER all the way up, kept from clipping by the limiter; MASTER then only sets the headphones (the right choice for an interface with no level control).
• The first time (and after an install), the computer sets the FM-1 up again as a MIDI + audio device: unplug and plug it back in if the input does not show. The MIDI port keeps its name.
• The audio input comes from Felucca 1.0, by way of SLOOP 2.3.

The web editor

Open it from the installer page (or the editor link) in Chrome or Edge, with the FM-1 on USB, and press Connect. It follows the device live: turn a knob on the FM-1 and the editor moves.

• Sound — the presets 01–20 and the voices of your bank 21–52, and every parameter of the selected track: the voice and its quick knobs BRITE / ATK / DEC / REL / FDBK, CUT / RESO, envelope, LFO, arp, sends.
• Voice — the whole DX7 voice on one page, in the DX7's colours: the algorithm drawn, all six operators with their envelopes (drag a point: across = rate, up / down = level), the pitch envelope, the LFO, the name. Every change plays at once; import / export single voices (.syx); store the bank.
• Sequencer — the steps; on the drum track a grid of 16 sounds × the steps, with levels and ratchets, and the kit.
• Tracks — the four channel strips.
• Library — your user presets and preset files, and your DX7 banks: pick one of the 8 banks, open or drop a .syx, see U01–U32 by name, erase it.
• Projects — the four projects, and Backup: Save a backup writes everything on the FM-1 to one file (the music in progress, the projects, the user presets, the settings and the DX7 bank); Restore from a file puts it all back (stop playback first).
• Settings — global, master (DUST, DUCK, FILT, ROLL), drums.

The protocol is documented in web/EDITOR_PROTOCOL.md (v12: SLOOP 2.3's backup, the bank upload, voice editing, the 8 banks, MY KIT, 128 steps; 4.0: the MIDI settings and your theme in the backup, SLOOP 2.7's LIVE command).

Compatibility

Device	M-VAVE FM-1 (SLOOP or the official firmware can be put back at any time)
Installer and editor	Chrome or Edge on Windows, macOS or Linux (they use Web MIDI with SysEx)
Cable	a USB data cable, plugged directly (no hub)
USB audio	any computer that takes a class-compliant USB audio input (no driver)
MIDI IN jack	3.5 mm TRS, through a TRS-to-DIN MIDI adapter (type A or B)
DX7 banks	32-voice bulk dumps (.syx, 4104 bytes); single-voice dumps go into a bank with any DX7 librarian first
Not supported	Bluetooth MIDI; a USB keyboard plugged straight into the FM-1

Troubleshooting

The installer or the editor does not find the FM-1. Use Chrome or Edge, a data cable, no hub, and allow MIDI access. Close every other app or tab that uses MIDI (a DAW, M-UPGRADE, another editor tab), then reload the page.

An install stopped half-way. The FM-1 waits in update mode: press INSTALL again. If sloopDX no longer starts, hold OCT− alone while switching on (USB RESCUE) and install again.

The black keys make no sound on a synth track. That track plays chords or the scale on the white keys: hold SEL (between FX and ENV) and set KNOB 1 CHORD to OFF and KNOB 3 KEYS to OFF. The drum track always uses the black keys.

Nothing plays from the MIDI IN jack. Try the other adapter type (A / B); check the keyboard's channel (1–3 synths, 10 drums, 4–16 the selected track).

The USB audio input does not show. Unplug the FM-1 and plug it back in (after an install the computer must find it again). In Audacity: Transport → Rescan Audio Devices. On Windows: Sound settings → Recording → show disabled devices.

The USB recording is too quiet, or follows the volume knob. Set HOME menu → USB AUDIO to FULL, or turn MASTER up.

Recorded notes move to the grid. sloopDX quantises what you record to the steps of the track (its DIV: 1/4 … 1/32, triplets, or since 3.3 1/2, a bar, two bars). For finer timing, set DIV to 1/32; for groove, use SWING.

Notes fade out on a dense part. The processor is at its limit: sloopDX fades one voice at a time (never the bass or the lead) rather than glitching. Fewer held notes help; 14 DX7 voices on this chip are still untested.

A .syx bank is refused. Only a 32-voice bulk dump (4104 bytes, with a valid checksum) loads. A single-voice dump (163 bytes) goes into a bank with any DX7 librarian first.

The lights or SYNC went back to OFF / INT. You went back to an earlier SLOOP, which does not keep them; set them again.

Something else? Open an issue: what you did, what you expected, what happened, and the version shown in HOME menu → ABOUT.

Specifications

Tracks	3 synth parts (8 DX7 voices shared) + drums (16 sounds, 6 DX7 voices)
Engine	DX7: 6 operators, 32 algorithms, rate / level envelopes with scaling, pitch envelope, LFO, feedback; integer port of Dexed's msfa (99 % of samples identical to Dexed, the rest within 1-2 LSB)
Sounds	20 factory voices + 32 from your .syx bank (U01–U32); macros BRITE, ATK, DEC, REL, FDBK; a low-pass CUT / RESO; 32 user presets
Drum kits	4 FM kits (DX KIT, 808 FM, ELECTRO, METAL) and MY KIT, 16 sounds each; 8 macros and a reverb send per sound, TUNE / DECAY locks per step, a noise operator, the dice; DRIVE and COMP on the drum bus
Sequencer	up to 128 steps per track from one pool of 256 for all four, own length and division each; chords with a level and ratchet per note; drums with a level and ratchet per sound; ties, slide; swing 0–100 (MPC 50–75 %); one sample-accurate clock (no drift)
Recording	live, quantised as heard (latency-compensated), overdub; free take (the tempo follows you) or the tempo set; start on the first note or a one-bar count-in; 1, 2 or 4 bars
Performance	layers: punch-in FX, erase, note repeat, step entry, key / chords, mute / solo / tap tempo, song sections
Effects	16 punch-in effects; master DUST, DUCK, DJ filter, limiter; per track drive, slicer, sends to a stereo chorus, a tempo delay and a stereo reverb
Memory	autosave, undo / redo, 4 projects, 32 user presets, one DX7 bank in flash, song of 4 sections × 16 steps × 1–64 bars, full backup / restore (editor)
Audio	44.1 kHz, fixed-point DSP (no floating point on the chip); USB audio input (the master output, 16-bit stereo, 44.1 or 48 kHz, class compliant)
MIDI	USB class-compliant in / out; TRS MIDI IN (3.5 mm); MIDI clock in (USB or TRS); DX7 bulk dumps via the editor protocol
Lights	button backlight (3 levels), C keys / white keys, played notes
Update	over USB from the browser (SHA-256 and CRC checked), USB rescue

Documentation

• SLOOP.md — the full manual (every page, layer, voice and kit)
• BUILDING.md — building, build options and tests
• TODO.md — open work
• web/EDITOR_PROTOCOL.md — the editor's SysEx protocol
• LICENSING.md — the licences of the code and the assets

Building and tests

See BUILDING.md: the JieLi toolchain (tools/get_toolchain.sh) and three files of the AC79 SDK, then ./build.sh (Linux / macOS) or INSTALL-SLOOPDX.bat (Windows with WSL), which builds the firmware and serves the installer and the editor on http://localhost:8766 (OPEN-EDITOR.bat opens the editor). To check the DX7 core against Dexed: MSFA=<dexed>/Source/msfa sh tests/dx7ref/build.sh.

tests/run_tests.sh runs the host test suite with no hardware: audio renders against golden hashes, CPU budgets, the sequencer's timing (no drift, swing, ratchets, rolls, the REC modes and the count-in, MIDI clock), the UI pages and layers, the knobs, flash storage, the update loader, MIDI and USB audio, the .syx import and the bank upload, the FM drum kits, and the web pages (editor, backup, installer).

Install the resulting .fwsc with python tools/fm1_install.py build/felucca.fwsc, or from the web installer; the installer page in docs/ (GitHub Pages) carries the current package.

Contributing

• Bugs and ideas: open an issue — what you did, what you expected, what happened, and the version in HOME menu → ABOUT. Reports from a real FM-1 are the most useful thing right now.
• Pull requests are welcome. Keep the style of the code around your change, add a host test when you can, and make sure tests/run_tests.sh passes. Do not submit Yamaha or M-VAVE voice data: every factory voice is designed in tools/gen_dx7_bank.py.
• By contributing you agree that your code is released under GPL-3.0, like the rest of sloopDX.

Credits and thanks

• sloopDX (the DX7 engine port, the FM drums, the fork): Sven Trogus.
• SLOOP by isod89 — the groovebox: the sequencer, UI, effects, storage, editor and installer; and in 2.3 the TRS MIDI input, the MIDI clock, the REC modes, the lights, backup and restore.
• Felucca by Leo Kuroshita (@kurogedelic) / Hügelton Instruments — the firmware SLOOP is built on, and the USB audio input, the knob reading and many fixes of Felucca 1.0 / 1.0.1 that came in with SLOOP 2.3.
• DX7 core: the msfa engine from Dexed (Apache-2.0; © 2012 Google, 2016–2025 Pascal Gauthier).
• Baud Girl (Madeline) — FM-1+VA showed how to edit FM on the FM-1: a list, SELECT for the row, ALGORITHM for the value. sloopDX's voice list follows that idea (no code: Baud Girl's firmware is closed source).
• @renebohne — the played-note key lights (SLOOP pull request #11), Program Change (Felucca PR #179), CC 74 on the cutoff (SLOOP #71). ChanceTheMaker and keremimo — the TRS MIDI input fix (Felucca Salt) and contributions to the MIDI clock.
• The second core (4.0): Andre Rezemini (andrerezemini, SLOOP pull request #111: the render split, the RAM below the RAM region), on the dual-core start of Charles Vestal's X0X (and its supply levels, X0X 1.0.9) and Kerem Kilic (keremimo)'s Melodee.
• From SLOOP 2.6 / 2.7 (4.0): INSERT, LFO SYNC / TRIG / POL, ENV SYNC, MIDI LEARN, the live drum mutes, the 1/4D delay, the THROWs and the arp modes after Felucca 1.4 / 1.5 / 1.5.1 (Leo Kuroshita); the knob acceleration and the LEVEL / PAN glide after JIANT FM by juanjiant-bit.
• Font: Terminus and Terminus Bold (SIL OFL 1.1). Icons: Fukiai (MIT, Hügelton Instruments). Interface ideas after teenage engineering's pocket operators and EP-133, Elektron's step entry and Akai's MPC (swing, note repeat, erase).

Licence

Code: GPL-3.0-only (see LICENSE, and LICENSING.md for the assets). No warranty. M-VAVE and FM-1 are trademarks of their owners; DX7 is a trademark of Yamaha. sloopDX is not affiliated with M-VAVE, Yamaha, teenage engineering, Elektron or Akai. No Yamaha or M-VAVE voice data is included.