VAWT - a virtual-analogue + wavetable machine for the Digitone mk1

A machine mod for the Elektron Digitone mk1 / Digitone Keys (OS 1.43 and 1.44). It adds a non-FM sound engine: saw/square/pulse/triangle/sine VA oscillators, a wavetable oscillator with bank switching (24 banks, all replaceable - factory ships 24 bundled tables), a sub osc, white noise, a wavefolder, bitcrush and a lowpass - played through the Digitone's own multimode filter, mixer, effects and AMP envelope, like FM.

Pick it per track from MACHINES (hold a track key T1–T4), like any machine. A sound's machine is stored in its sound slot 0, so sound locks switch engines per trig, and p-locks, LFOs, MIDI CC and presets work on its knobs as on FM. Polyphony safety fuse: VAWT is monophonic - at most 1 VAWT note renders at once (newest note wins) - further simultaneous notes stay silent until the slot frees.

Controls

SYN1's first page and SYN2's first page become VAWT's (second pages stay FM's and show blank). All values are the stock parameters', so everything persists with the sound. Coarse tuning is OCT in whole octaves; fine transpose lives on the TRIG page. Knob D is our own parameter 182 (stock 110 only spans 0–2); the overlay's tick points SYN1-D at 182 on a VAWT track and back at stock 110 on an FM one, since the page table is shared and built once. Knob A stays the stock parameter 107, whose 0–7 range is the documented 1–8. If a knob misbehaves on sounds from older builds, re-pick VAWT from MACHINES to reset the sound.

SYN1 page	SYN2 page

SYN1 (top row left to right, then bottom row):

• A - WAVE (box reads 1–8): the oscillator. 1 SAW, 2 SQU (square), 3 PLS (pulse), 4 TRI (triangle), 5 SIN (sine), 6 WT (wavetable, see TABL), 7 NOI (noise), 8 off (main oscillator silent - play SUB and NOIS alone). Stock parameter 107; FM tracks keep stock ALGO untouched. (param:183, a 0–6 clone that would drop the silent 8th slot, is minted but not bound.)
• B - SYM (blank dial): wavefolder symmetry −100…+100%, middle = symmetric folds. Offsets the fold for even harmonics and lopsided folding; pairs with FOLD. Only audible when the folder works (FOLD up and/or SYM off middle).
• C - UNIS (blank dial): second-oscillator mix 0–100%. A detuned twin of the same wave; 0 = single oscillator.
• D - OCT: octave −2 / −1 / 0 / +1 / +2. Coarse tuning. Stops at both ends.
• E - DET: twin-oscillator detune, ±52 cents, middle = in tune. Only audible with UNIS turned up.
• F - FOLD: wavefolder 0–100%. Folds the waveform back on itself for brighter, harsher harmonics.
• G - SUB: rounded-square sub level 0–100%, an octave below (see SOCT). Mostly square so it cuts through, with triangle mixed in to round the edges.
• H - NOIS: white-noise level 0–100%, full-strength at max.

SYN2 (short labels; the envelope graphs are FM leftovers that do nothing):

• A - PW: pulse width 5–95%. Only shapes SQU and PLS.
• B - WPO (= WPOS): wavetable position 0–100%. Set WAVE to 6 (WT), then turn this to morph through the TABLE bank's 8 frames. Does nothing on other waves.
• C - DRF (= DRFT): analog pitch drift 0–100%. Slow random detune.
• D - TON (= TONE): lowpass 0–100%. Full = wide open.
• CRS (= CRSH): crusher, OFF at full clockwise, then 12-bit/18 kHz down to 4-bit/5 kHz as it turns down. Depth and rate degrade together.
• SOC (= SOCT): sub octave −2 / −1 / 0, relative to the oscillator.
• TABL (= TABLE): wavetable bank 1–24. Instant switch, persists and p-locks like any knob. Bake a folder of your own instead: docs/custom-tables.md.
• P: unused.

The "RATIO" heading, SYN1's algorithm diagram and SYN2's envelope graphs are FM leftovers the framework cannot redraw per track. WAVE's 1–8 map above; the rest show their native graphics.

LFOs

Both system LFOs modulate all 15 VAWT SYN slots, like on FM - FM tracks are unaffected. The destination list still shows FM names (upstream limit), but each entry targets the same sound slot VAWT uses, so pick by position: e.g. HARM moves DET, ALGO moves WAVE, and so on down the SYN knob order. Depth adds to the knob value and clamps at the knob's stock range. FILTER and AMP destinations are not applied in the VAWT render - they act downstream in the Digitone's filter/mix, as on FM.

Signal path

OSC1 (WAVE @ pitch+OCT+drift) ────────┐
OSC2 (same WAVE, +DET, +drift) ───mix─┤─→ fold → crush → lowpass → out
SUB rounded-square (@ sub octave) ────┤         (then Digitone filter/mix/FX,
white noise ──────────────────────────┘          AMP envelope + velocity)

Output peaks at DNM_PEAK, about as loud as FM at stock defaults. Zeroed stages are skipped exactly, so a default patch costs well under a full one.

Status

• Host DSP tests pass (python3 tools/vawt_host_test.py, 40 checks - needs an elekloader checkout at tools/elekloader for headers only, no stock needed): pitch, octave, transpose, fold, wavetable morph and bank switching, pulse width, sub, noise, tone, crush, levels, bounds, plus both system LFOs to VAWT SYN slots (OCT doubling, FOLD, clamp, FILTER-ignore). LFO destinations show FM names but modulate the same slots; FILTER/AMP LFOs work downstream as on FM.
• Emulator: boots in digiemu vs stock.
• Hardware: tested on a Digitone mk1 (1.43 and 1.44 builds); flash at your own risk. The bootloader is never touched, so the stock .syx always recovers the unit (FUNC on power-up → TRIG 4 OS UPGRADE).

Build

You need the stock OS .syx (Elektron's download), the m68k toolchain, and an elekloader checkout at tools/elekloader with core/machines sources (separate project, not included here):

export ELEKLOADER_CROSS=m68k-elf-
STOCK=path/to/Digitone_and_Digitone_Keys_OS1.43.syx
EL=tools/elekloader
python3 -m elekloader.sdk.build $EL/mods/core-dn1 --stock $STOCK
python3 -m elekloader.sdk.build $EL/mods/machines-dn1 --stock $STOCK
python3 -m elekloader.sdk.build vawt --stock $STOCK
# or: sh scripts/build.sh $STOCK

scripts/build.sh builds all three and lints + patches a test image into out/ (local build output only, not in git).

Bake your own wavetables: docs/custom-tables.md.

Pages

On a VAWT track the SYN1/SYN2 content is fully ours: an 8-knob grid per page with our labels, true value texts and mini bars, tracked from the kit every frame (p-locks and presets included). The last-turned encoder's cell gets a frame. Title bar, left rail and status stay stock.

Gating uses firmware state, not pixels: paint only when the active track's sound plays VAWT, the showing key is SYN1/SYN2, no screen sits over the pages, and the shown view is on its first page. Holding a sequencer step keeps the overlay up and shows that step's parameter locks instead of the kit (hardware-proven slot-indexed, inverted where locked). Holds address steps only in GRID or STEP record; otherwise the trigs play notes and the kit shows, as stock. Copy/paste/ clear toasts yield the frame while the firmware's message shows. ev_tick re-arms the frame only when something shown changed, so the UI idles when nothing moves.

Known limits (upstream, not VAWT): the turn popup's long name, the LFO destination lists and the page group headings read the stock parameter records, so a turned DET reports Harmonics=… and WAVE reports Algorithm=… up top. Only the name stays FM's - a machine mod cannot rename those per track.

Files

Licence: GPL-2.0-or-later. Unofficial, not affiliated with Elektron.