Scale Remapper

A client-side web app for remapping any Scala tuning scale onto any other. Load Scale A (your pitch palette) and Scale B (your destination grid); each degree of B snaps to the nearest pitch in A. Export the result as a single .scl file with B's note count and period, whose interior pitches come from A.

Built with TypeScript + Solid.js. Pure client-side — nothing leaves your browser.

Why

The default session is the familiar 12-key workflow: B starts as 12-EDO, so loading a source .scl and remapping produces a 12-note scale whose pitches are borrowed from your source. Play C–C♯–D… on a keyboard tuned with the output and the notes sound like they came from the source scale — the familiar 12-key layout, retuned.

But B isn't fixed to 12-EDO. Swap in any .scl or a built-in EDO preset and the same engine maps B's grid onto A's pitches. A few examples:

• JI → 12-EDO (the default flow): load a just-intonation .scl as A, leave B at 12-EDO. Each of the 12 keys snaps to its nearest JI value.
• JI → 31-EDO: same A, pick the 31-EDO preset for B. Output is a 31-note scale, each pitch snapped to the nearest JI value.
• 12-EDO → Bohlen-Pierce: A = 12-EDO, B = a Bohlen-Pierce .scl. Output is a 13-note scale with BP's 3/1 tritave period (1901.955¢), interior pitches taken from the nearest 12-EDO values. Non-octave periods are fully supported.

Features

• Two independent scales. Scale A (source palette) loads from a .scl file. Scale B (destination grid) defaults to 12-EDO and can be replaced by a loaded .scl, a built-in EDO preset (12, 19, 22, 31, 41, 53), or reset to the 12-EDO default with one click. Parser is hand-rolled client-side (the format is small enough to implement directly, ~30 lines).
• Auto-Map — one click snaps every B-degree to its nearest A-pitch.
• Manual connect — drag from a dot on one ring to a dot on the other to wire up individual degrees. Mix freely with Auto-Map to nudge after the bulk pass.
• Concentric-circle visualization — outer ring = Scale A, inner ring = Scale B, both data-driven for any degree count, with deviation-colored connectors, hover tooltips, tie ghosts, and collapse flagging (when several B-degrees land on the same A-pitch).
• Click-to-audition — a built-in Web Audio synth (sine, square, triangle, saw) lets you A/B a remapped pitch against B's pure pitch.
• Live preview — a read-only panel shows the resulting scale two ways (readable deviations and raw .scl text), refreshing on every change.
• Save — download a single .scl with B's note count and period; the period echoes B's last entry verbatim (e.g. 2/1, or 3/1 for Bohlen-Pierce).

Out of scope by design: MIDI input, live keyboard playing, .kbm export, multi-period output, scale editing (load or pick — you can't add/remove degrees by hand), a scale library beyond the small EDO preset list, and any backend/accounts/storage.

Getting started

Requires Node 26 (CI runs on 26).

npm install
npm run dev      # start the dev server

Open the printed local URL, drop in a .scl, and start remapping.

Commands

Command	Description
npm run dev	Start the Vite dev server
npm run build	Type-check and build for production
npm run preview	Preview the production build locally
npm test	Run the test suite once
npm run test:watch	Run tests in watch mode

Testing

The suite covers the parser/serializer, mapping logic (auto-map, deviation, displacement), audio and audition controllers, and component behavior via @solidjs/testing-library, plus a smoke test that round-trips a real .scl (see test-fixtures/). Run npm test.

License

See THE-LICENSE.txt.