skafinity

ska + infinity — an endless, deterministic procedural ska / reggae-rock track that's generated entirely in your browser from a short shareable seed. No server, no audio assets: the music is synthesised from scratch in C# (compiled to WebAssembly) and scheduled through the Web Audio API. The whole song is a URL — …/web/#vibe:tag:n.

The engine is the same MusicGen.cs + VibeCodec.cs the Rotaliate s&box music library ships (sbox-library/). The web toy compiles that shared source to WebAssembly with the .NET wasm-tools workload — no port, so the game and the web run identical composition code. reference/ keeps the original C# for context (see CLAUDE.md).

Build & run

One-time toolchain (machine, not vendored):

sudo apt-get install -y dotnet-sdk-10.0
dotnet workload install wasm-tools

Then:

make          # publish the engine → web/_framework  (AOT; ~2 min)
make dev      # same but skip AOT — much faster to build, identical composition
make test     # node smoke test of the JS↔wasm boundary (needs web/_framework/)
make serve    # static server rooted at web/; open http://localhost:8000/

The page must be served (the .NET runtime is a bundle fetched over http) — opening web/index.html via file:// won't work. web/ is self-contained (it includes web/_framework), so deploy it by pointing any static server's docroot straight at web/. web/_framework is committed so a fresh clone is testable with just make serve; rebuild it with make. A single self-contained .html (inlining the runtime) is a deferred follow-up — make dist.

What's here

Path	Role
sbox-library/Skafinity/Code/MusicGen.cs	Composition (fixed RNG draw order) + subtractive synth — the algorithmic source of truth, shared with the s&box library.
sbox-library/Skafinity/Code/VibeCodec.cs	Base-36 vibe encode/apply + field metadata (append-only wire format).
wasm/Exports.cs	The [JSExport] boundary (generate, vibe codec, WAV, config) — the only web-specific code.
wasm/Skafinity.Wasm.csproj	browser-wasm project that <Compile Include>s the shared .cs and builds the runtime.
web/engine.js	Boots the .NET runtime and adapts the exports to the small mod API the app uses.
web/index.html · app.js · worker.js · style.css	The page: Web Audio crossfade scheduler, rolling playlist, vibe editor, WAV export, shuffle.
sbox-library/Skafinity/skafinity.config.json · web/config.json	The shared house-mix config (peak balances / kit presence / stereo-width knobs). Canonical in the library; make copies it to web/. Overlaid at runtime — retune the baseline mix or the width without a rebuild.
test/smoke.mjs	Node smoke test that boots the published runtime and exercises every export.

Features

• Rolling playlist — n auto-advances on every crossfade and is persisted; a full playlist panel shows played / now-playing / up-next, with click-to-jump and per-song export.
• Export to disk — generate the loop as an interleaved-stereo WAV in-browser and download it (no server).
• Share via URL — the seed lives in location.hash, so a reload or a shared link reproduces the exact same song.
• Random every song — a 🎲 toggle that re-rolls the vibe and the genre for each new song (keeping your per-voice volumes), so the stream keeps reinventing itself.
• Stereo image — the mix is laid out across the field, not summed to the centre: hats left / ride right, toms spread by pitch (rack → left, floor → right), the kit's two crashes split L/R, and every non-drum voice is double-tracked — two slightly-detuned, independently-phased takes panned apart for genuine width (not a mono copy on both channels). Bass stays centred for a tight low end. The STEREO WIDTH knob scales the whole image from full down to mono, and the double-tracking parameters are config-tunable below.
• House-mix config, no rebuild — the baseline peak balances and the stereo-width knobs live in web/config.json (copied from the shared sbox-library/Skafinity/skafinity.config.json); edit + reload to retune the mix or the width without recompiling the wasm. These shape the baseline mix and are not vibe knobs, so they never travel in the seed.

Instruments & their inputs

The vibe editor is a matrix: a block of global knobs that shape the whole track, then one row per instrument, four columns each (volume / tone / character / extra). Every knob is quantised to one base-36 digit (16 levels) in the seed. The instrument roster — and the two genre-specific knobs in each row — changes per genre; the field list is read straight from VibeCodec.cs, so this table is just a readable mirror of it.

Global (all genres): TEMPO MIN / TEMPO MAX (BPM band, 60–200) · TEMPO BIAS (how often a song lands fast) · SWING (off-beat delay, 0–0.4) · RESONANCE (filter Q, 0.2–2) · STEREO WIDTH (master stereo amount — see Stereo image below; 100% = full, 0% = mono).

Every instrument row shares the first two columns: VOLUME (0–150%) and TONE (low-pass cutoff). DRUMS carries the same four knobs in every genre — its TONE sweeps toms ↔ cymbals, and its character/extra are BUSY (fill/hit density) and DRIVE (timing feel, pull ↔ push) — but the underlying beat changes per genre, so it's listed in each table below. The other rows' character/extra columns differ by genre:

Ska — BASS · SKANK · ORGAN · LEAD · HORNS · DRUMS

Instrument	Character	Extra
BASS	OCTAVE POP (octave jumps)	TRIPLETS
SKANK	BITE (high-pass)	CHOP (note length)
ORGAN	BUBBLE (chance)	VIBRATO (depth)
LEAD	JUMPINESS (melodic leaps)	TRIPLETS
HORNS	SECTION (full-section chance)	DENSITY
DRUMS	BUSY	DRIVE — one-drop or stepper groove (backbeat when fast)

Rock — DRUMS · BASS · KEYS · LEAD GTR · RHYTHM GTR

Instrument	Character	Extra
DRUMS	BUSY	DRIVE — straight backbeat, per-song kick accents
BASS	DRIVE (overdrive)	OCTAVE POP
KEYS	DISTORTION	CHUG
LEAD GTR	DISTORTION	BENDINESS
RHYTHM GTR	DISTORTION	CHUG

Country — DRUMS · BASS · RHYTHM GTR · KEYS · LEAD GTR

Instrument	Character	Extra
DRUMS	BUSY	DRIVE — train-beat backbeat, per-song kick accents
BASS	DRIVE (overdrive)	OCTAVE POP
RHYTHM GTR	DISTORTION	CHUG
KEYS	DISTORTION	CHUG
LEAD GTR	DISTORTION	BENDINESS

Same per-instrument columns as Rock, but over a much cleaner base distortion (honky-tonk piano, strummed open chords, twangy telecaster leads with heavy BENDINESS).

Metal — DRUMS · BASS · RHYTHM GTR · LEAD GTR

Instrument	Character	Extra
DRUMS	BUSY	DRIVE — double-kick gallop
BASS	DRIVE (overdrive)	OCTAVE POP
RHYTHM GTR	DISTORTION	CHUG
LEAD GTR	DISTORTION	BENDINESS

Same columns again, but a heavy base distortion: palm-muted gallop rhythm (CHUG) and fast shredding leads.

The straight backbeat (Rock, Country, and fast Ska) picks a per-song kick accent personality — which off-beats the kick leans into beyond beats 1 & 3 — and rolls each accent per bar, so the groove breathes instead of stamping one mechanical pattern every bar.

Parity

Same seed ⇒ same song — and because the web toy compiles the same MusicGen.cs as the s&box library, a seed shared from one plays identically in the other (no port to drift). make test boots the published runtime under node and checks generation, vibe round-trip, determinism, and WAV output.