CULTBOX

CULTBOX turns the M-Vave FM-1 into a three-channel filth machine containing: a Polivoks-style synth (PLVKS), a dub siren (DUBMARINE) and a vintage drum machine (DRUMS), all sounding at once through shared echoes and per-channel effects.

What is in the box:

• PLVKS: a duophonic voice modelled on the Formanta Polivoks, with Mono, Duo and Unison modes, a step sequencer, an arpeggiator and scales.
• DRUMS: ten single hits sampled from the legendary Elka Drummer One drum machine with a step sequencer and a sine sub under the kick.
• DUBMARINE: a dub siren with a radar-style screen, played from the keys.
• Mixer: one level and one echo send per channel, plus a master level.
• Effects: two BBD-style echoes that can sync to tempo, and on every channel a vintage control, five saturation models and a tape stage.

Your first five minutes:

1. Switch on. The boot logo shows, then the mix page: a black-on-white logo above four squares for channels 1 to 3 and the master.
2. Play drums. Click ALGORITHM once to select DRUMS (channel 1). The first ten keys play the ten pads.
3. Make a beat. Press SEQ. The white keys are the 16 steps of the bar: tap a key to switch a step on, black keys choose the pad. Press PLAY to start.
4. Add a bass. Click ALGORITHM to PLVKS (channel 2), turn PRESETS to pick a sound such as ACID BASS or SUB BASS, and play the keys. Press SEQ to sequence it the same way.
5. Balance it. Press HOME to return to the mix page, then turn KNOB 1 to 4 for the DRUMS, PLVKS and DUBMARINE levels and the master.

The rest of this manual covers each part in turn: the panel, the mix page, the three engines, the effects, patterns and MIDI, and installation.

Every control keeps one meaning across the three engines: the four KNOBs always edit the four values on screen, and the section buttons jump between pages.

Knobs and dials

Buttons

Keys

The 27 keys run from F3 to G5. On PLVKS and DUBMARINE they play notes. On DRUMS the first ten keys are the ten pads and the octave buttons do not move them. In SEQ the white keys become the 16 steps of the bar and the black keys choose the pad (DRUMS).

Section buttons by engine

The mix page is the home screen: the first stop of the ALGORITHM dial, and where HOME takes you from anywhere. All three engines sound at once, and this page balances them.

The screen shows the logo above four squares: CH 1 DRUMS, CH 2 PLVKS, CH 3 DUB and MIX MASTER. Each square has a level bar, and the three channels also show a small meter of what is sounding now. The channel the keys currently play has a white frame.

SELECT switches between three pages, named on the screen:

How the routing works:

• DRUMS and PLVKS share echo 1. DUBMARINE has its own echo 2, so a dub siren can ring out without washing the beat.
• Sends are taken after each channel's level, so turning a channel down also turns its echo down.
• Each channel's effects (vintage, saturation, tape) come before its level and its send.
• Levels, sends and master are part of your setup and are not stored in presets. They are kept in flash when you stop editing.

The PAN page places each channel in the stereo field, from L100 through C (the centre) to R100. Every pan starts at the centre. The fourth square is the shared delay, labelled DELAY ECHO, so the echo that DRUMS and PLVKS share can be placed on its own; the master has no pan. The bar grows out from a centre mark, and a knob turn stops at C on its way across.

• Two voices into two mixer channels: pan DRUMS hard left (L100) and PLVKS hard right (R100) and take the FM-1's stereo output to a stereo-to-two-mono Y cable. At L100 the right side is silent, and at R100 the left side is.
• The shared delay stays in stereo at the centre. As you pan it away it blends to mono and sits on that side; at either end it is fully mono.
• DUB's pan moves its own echo with it.
• Pans are part of the setup, like levels and sends: not stored in presets, kept in flash.

From the mix page, one click of ALGORITHM selects DRUMS. Pressing SEQ there opens the pattern of the track that is currently selected (DUBMARINE has no sequencer).

PLVKS is a duophonic synth modelled on the Formanta Polivoks: two oscillators into a saturating state-variable filter, with a looping envelope, a modulator and a drive stage that overloads the filter input. Select it with ALGORITHM (channel 2). Its screens are styled after the Polivoks panel, and a red lamp lights when a note sounds.

Pages

Turn SELECT to move through the pages, or use the section buttons. Values run 0 to 127 unless a choice is listed.

The remaining PLVKS pages are the arpeggiator and scale (see the next section), the BBD echo and echo sync, and the Character and Tape effects (see Effects).

Voice modes

• Mono: the last key you press plays both oscillators.
• Duo: the lowest held key plays oscillator 1 and the highest plays oscillator 2, so two held notes sound together. This is the Polivoks' duophonic mode.
• Unison: both oscillators play the same note, with the Detune value split either side of it for a wide, fat tone.

Things worth knowing

• Gate On holds the last note after you let go of the key, so the envelopes can run on their own.
• Loop restarts the attack each time the decay settles onto the pedestal, so the envelope cycles for as long as the key is held. Choose Filter, Amp or Both.
• Glide slides oscillator 1 between notes. A slide step in the sequencer (see the next section) glides both oscillators.
• Drive overloads the filter input unevenly, adding even harmonics and warmth.
• Bend and mod wheel: MIDI pitch bend moves two semitones either way; the mod wheel (CC1) adds vibrato and filter wobble; CC64 is the sustain pedal.
• The voice drifts slightly on its own, as analogue gear does. The VINTAGE control (see Effects) pushes that much further.

Presets

PRESETS selects from 21 factory sounds (F1 to F21) and 16 user slots (U1 to U16). A preset loads only the sound of the selected engine, so the other channels keep playing. The twelve PLVKS factory sounds are INIT, SCREAMER, ACID BASS, SUB BASS, SOLID PAD, FM BELL, BUZZ ORGAN, DRONE, ZAP, WOBBLE, ARP LOOP and WIND. Press SAVE to store your own into the selected user slot (or the next free one). Presets hold the voice and the BBD echo of that engine; the mix, per-channel effects, sub, arpeggiator and scale settings are kept separately.

The sequencer

Press SEQ to enter the sequencer. The sixteen white keys become sixteen steps; a lit step plays. Press a key to switch its step on or off. PLAY starts and stops the pattern. Each track (PLVKS, DRUMS) has 16 pattern slots, and the pattern is saved automatically about two seconds after you stop editing while the sequencer is stopped.

Two pages set up the pattern:

With Sync set to Ext the sequencer follows incoming MIDI clock instead of its own tempo.

HOME chords inside the sequencer

Hold HOME and press another button:

• HOME + SEQ: clear the current pattern.
• HOME + ARP: copy the current bar into the next one.
• HOME + SAVE: save the pattern now.

Step edit

Hold a step key and press EDIT to open that step. SELECT walks from step to step, the white keys move the cursor, and the 8x8 dot map shows where you are in the pattern. The knobs edit the step:

OCT- and OCT+ switch between the two pages. Note 2 gives the step a second note for duophonic voicing. Slide glides into the step. Chance is the probability that the step plays, and Delay pushes it later within its slot. With a scale chosen (see below), the note knobs walk scale degrees instead of semitones, up to three degrees per click, so every note you land on is in key.

Arpeggiator

Press ARP to switch the arpeggiator on. Held keys then play one after another instead of together. The arpeggiator runs on the sequencer's tempo and starts on the next step of a running pattern, so it stays in time. It sits on the PLVKS GLO and FX pages:

• On: the arpeggio plays while keys are held and stops when you let go.
• Latch: the chord keeps playing after you let go. The next key you press starts a new chord.
• Order plays the notes in the order you pressed them; the other modes sort low to high. Up to eight held notes are used.

Scale and live quantize

The SCALE page sets a Root (C to B) and a Scale: Chroma (no scale), Major, Minor, Dorian, Phryg, Lydian, Mixo, HarmMn, PentMj, PentMn, Blues or Whole. Two switches decide what it does:

• QKeys snaps notes you play (keys, MIDI and the arpeggiator) to the scale. A note between two scale notes goes to the lower one.
• QSeq snaps the pattern's notes to the scale as it plays. The stored pattern is not changed, so turning it off brings the original notes back.

Recording

Press REC (outside the sequencer) to arm recording. When the pattern runs, whatever you play, including arpeggios, is written into the steps it lands on. Notes you audition while editing a step are played raw, so they are not arpeggiated or quantized.

DRUMS is a ten-voice sampled drum machine (channel 1 on the ALGORITHM dial). Outside the sequencer the keys play the pads; the factory kit is ELKA KIT (F21), and seven ready-made grooves are waiting in the first pattern slots (see Patterns, saving, tempo and MIDI).

The pads

A closed hat cuts off an open one (the Choke setting, below). Keys hit harder the harder you play them when your keyboard or MIDI source sends velocity.

Pages

The BBD echo, echo sync, Character and Tape pages follow (see Effects). PAD edits one voice at a time: pick it with KNOB 1, then shape it. Crush reduces the bit depth for a gritty, lo-fi sound; Tone is a master brightness control for the kit.

Kick sub

The kick is a sampled hit, and the KICK SUB page adds a pure sine oscillator underneath it for weight. It starts in phase with the hit so it never cancels the sample's attack.

• Sub level: how much sub is added. It is 0 by default, so existing kits sound unchanged.
• Tune: the pitch, from about 30 Hz to 120 Hz.
• Decay: how long it rings, from 40 ms to about a second.
• Drop: how far the pitch falls at the start, for the classic 808 "boom".

The sub follows the kick's velocity and level, and sits after Crush and Tone so those do not thin it out. Its level is capped well below full scale, so turning it up will not overload the output.

Drum sequencer

Press SEQ with DRUMS selected. Each of the sixteen keys is a step, and the pad you have chosen is the voice you are programming: press a step to toggle that voice on it. The TIMING and PATTERN pages work as they do for PLVKS (Tempo, Swing, Length, Rate, Pattern slot, Sync, Hit, Accent), and the HOME chords (clear, copy bar, save) are the same.

Hold a step and press EDIT to open its step edit page:

Chance sets the probability that the hit plays. Ratchet repeats the hit several times inside the step for rolls and flams. Delay pushes the hit later within its step for a loose, human feel.

DUBMARINE (channel 3) is a dub siren after the DUBMARINE web app: a saw oscillator whose pitch is swept by an LFO, through a resonant low-pass filter, with its own echo. Its screens are styled like a radar sweep. It is a live instrument and is not sequenced, so it can sound over a running drum and PLVKS pattern.

Playing it

The keys set the pitch the siren plays from. Hold a key to sound it and let go to stop; Hold sets how long the sound stays after you release. Glide slides the pitch between keys, which stands in for the XY pad of the original.

Pages

The BBD echo, echo sync, Character and Tape pages follow (see Effects).

• Shape chooses the LFO wave: Sine, Square, SawDn, Tri, Warble, NarPls, Stairs or S&H (sample and hold).
• Sweep moves the filter during the note. SweepTo chooses what it moves: Filter alone, or Filter plus Tune.
• Decay fades the sound after you let go; Hold keeps it sounding for a time after release.

Presets and echo

The DUBMARINE factory sounds are CLASSIC SIREN, SIREN WARBLE, POLICE, DOWN SWEEP, LASER, STAIRCASE, RANDOM CHIRP and DUB DROP (F13 to F20). Selecting one loads only the siren, so the drums and PLVKS keep playing.

DUBMARINE has its own echo, separate from the one that serves the drums and PLVKS. On the mix page its send goes to that second echo, so you can ride the siren into long dub repeats without smearing the beat.

Every engine has the same four effect pages at the end of its page list: BBD ECHO, ECHO SYNC, CHARACTER and TAPE. Everything starts switched off, so a new sound is clean until you turn something up. Effect settings belong to the channel and are not stored in presets, so changing preset never changes your echo or tape.

BBD echo and echo sync

The echo is a bucket-brigade delay: dark, soft repeats that smear as they repeat. There are two. The first serves the drums and PLVKS, and the second serves DUBMARINE.

The ECHO SYNC page locks the echo time to the sequencer tempo, so repeats fall on the beat and follow tempo changes. Choose a note value from 1/32 up to 1/2, including triplet and dotted values. With sync off, Time sets the delay freely. How much of each channel reaches the echo is set by its send on the mix page.

Character

CHARACTER holds two stages that colour a single channel:

• Vintage darkens the sound a little. It also makes the voice itself drift: pitch and filter wander slowly, and each note is tuned slightly differently, as in old analogue gear. The drums vary each hit's pitch and level a little. At zero, nothing changes.
• Model and Drive set the saturation, and Mix blends it with the clean sound. The models are:

Saturation is oversampled to keep it clean and holds the level steady, so turning Drive up changes the tone rather than the loudness.

Tape

TAPE models a worn tape machine:

• Drive pushes the tape into soft saturation.
• Wow adds slow pitch wobble and quicker flutter.
• Age rolls off the highs, and thickens the low end with a head bump.
• Mix blends the tape with the clean sound.

Each channel (DRUMS, PLVKS and DUBMARINE) has its own Character and Tape settings, and a stage that is switched off costs no processing. The order is saturation, then tape, then vintage.

Patterns

DRUMS and PLVKS each keep 16 pattern slots, chosen with the Pattern knob on the PATTERN page of the sequencer. Switching slots saves the one you were editing first. A pattern remembers its steps, length, rate, Hit and Accent. Tempo and swing belong to the song and are shared by both tracks. They are not stored per pattern, apart from the factory patterns below.

Patterns save by themselves about two seconds after you stop editing, provided the sequencer is stopped, because saving briefly interrupts the sound. SAVE (or HOME + SAVE) in the sequencer saves at once.

Factory drum patterns

The first seven drum slots come loaded with classic grooves. Choosing one shows its name and sets the tempo it was meant for.

Each is one 16-step bar at 1/16. They use the kick, snare, closed and open hats, and the Clave pad for the side stick in the reggae patterns. The Steppers, One-Drop and Rockers grids also carry an accent on beats 1 to 4, which plays as accented hits. They are ordinary patterns: edit them and the changes are kept (the name is dropped). If a slot already held your own pattern when you updated, yours stays and that factory pattern is skipped. Slot 16 is always left free.

Sound presets

PRESETS selects a factory (F1 to F21) or user (U1 to U16) sound and loads it as you turn the dial. An asterisk marks a sound you have changed. SAVE stores the sound in the selected user slot, or in the next free slot when you start from a factory sound. Presets cover one engine's voice, so patterns, the mix and the effects are never changed by a preset.

Tempo and sync

Sync is Int (the sequencer's own tempo, 40 to 240 BPM) or Ext (it follows incoming MIDI clock). The echo sync and the arpeggiator both run on whichever tempo is active, so everything stays together.

MIDI

The FM-1 listens on one MIDI channel, set with PLAY + ALGORITHM (OMNI by default). It responds to:

• Notes to the engine you have selected. The DRUMS use the General MIDI notes in the pad table.
• Pitch bend of two semitones, mod wheel (CC1), sustain pedal (CC64) and all notes off (CC123).
• Program change, which selects the preset.
• MIDI clock, when Sync is set to Ext.

Notes you play through MIDI follow the arpeggiator and scale settings in the same way as the keys.

Installing CULTBOX

CULTBOX is a firmware package named cultbox.fwsc, with the package identity FM-1_333. Download it from the latest release on the project's GitHub page, https://github.com/beatcult/cultbox/releases/latest (direct link: https://github.com/beatcult/cultbox/releases/latest/download/cultbox.fwsc). Install it in one of these ways:

• Use the FM-1 Firmware Hub (https://thefirmwarehub.com) or another web installer that accepts a .fwsc file.
• Run the installer tool from the repository: python3 tools/fm1_install.py cultbox.fwsc. It connects over USB, asks before it writes anything, and restarts the FM-1 into the new firmware.

To leave CULTBOX, install any other firmware the same way: the update loader is part of the package. If CULTBOX ever crashes at start-up, hold OCT- while switching on for the USB rescue (no sound, only the updater). CULTBOX works with both flash chips found in FM-1 units, the Puya P25Q80 and the UC25HQ80 fitted to units sold since autumn 2026.

Do not unplug the FM-1 while it is writing. The installer checks the package before it starts and refuses damaged files.

Building it yourself

The README in the project describes the toolchain. ./build.sh produces build/cultbox.fwsc and fails on anything that would stop the FM-1 from starting. The host simulator, tests/run_host.sh, runs the firmware on a computer, writes the sound to a WAV file and saves screen pictures, which is handy for trying changes without the hardware.

Troubleshooting

Quick reference

• Switch engines: ALGORITHM dial. MIX (home), DRUMS, PLVKS, DUBMARINE.
• Back to the mix page: tap HOME.
• Sequencer: SEQ, PLAY, hold a step + EDIT for step edit.
• Sequencer chords: HOME + SEQ clear, HOME + ARP copy bar, HOME + SAVE save.
• Arpeggiator: ARP button, Latch on the PLAY page.
• Record notes into the pattern: REC, then play while the pattern runs.
• Save a sound: SAVE (selected user slot or next free one).
• Sound reset: hold HOME 1.5 seconds outside the sequencer.
• USB rescue: hold OCT- while switching on.