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The deepest audio lever: a score carries no recording, only note events. A deterministic trig-free reference synth (phase-accumulator oscillator + linear ADSR, all in the Fx floor) reconstructs a canonical i16 PCM mixdown; conformance is mixdown-equivalence, the music counterpart of spatial audio. A soundfont/neural instrument is the sink's presentation. - wai-rs `score` feature: WSCR container + reference synth + mixdown/ score hashes; corpus (scale/chord/arp) via wai_score_vectors; registered + tiered Lossless. - wai-web ScoreSink + the /score browser sink (in-tab verify + Web Audio). - extensions/score.md, SPEC §5 row, content-taxonomy music → ✅. Green: wai-rs all features (68 lib + integration) + clippy, wai-web wasm. Co-Authored-By: Claude Opus 4.8 <[email protected]>
105 lines
4.2 KiB
Markdown
105 lines
4.2 KiB
Markdown
# WAI Extension: Score (Music as Instructions)
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> Status: Draft. Phase 6 — the deepest audio lever. Ship the
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> composition, not the recording: a score of note events the sink
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> synthesizes. Conformance is **mixdown-equivalence**, the music
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> counterpart of spatial audio. Reference impl: the `score` feature of
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> `wai-rs`; corpus: `score-conformance/`; live sink:
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> wai.transaction.science/score.
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Keywords **MUST**, **MUST NOT**, **SHOULD**, **MAY** are RFC 2119/8174.
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## 1. Scope and model
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A `wai.audio.score` object carries **no recorded audio** — only note
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events. Where `wai.audio.scene` mixes recorded sound *objects*, a score
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is reconstructed from instructions: a deterministic reference synth
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turns the notes into a canonical PCM mixdown, and a sink with a richer
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instrument (soundfont, neural) renders the same score for presentation.
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It is lever 3 (instructions-at-the-sink) for music — a minute of music
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is kilobytes of notes, not megabytes of samples.
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In scope: the container, the note model, the deterministic reference
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synthesis, the **mixdown-equivalence** conformance criterion, the
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receipt profile. Out of scope: a transport; the sink's instrument
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(soundfonts, neural synths — presentation, not conformance); MIDI-file
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import (an authoring concern).
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Relationship to the core spec: mirrors spatial audio. The reconstruct
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runs in the `wai.det.fixed64` floor; `media` takes the value `"audio"`;
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`wai.audio.score` is authoritative.
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## 2. Container (`WSCR`)
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```
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"WSCR" | u16 n_sections | section table (u8 kind, u32 off, u32 len) | sections
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```
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| kind | section | required |
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|---|---|---|
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| `0x01` | contract (canonical JSON) | REQUIRED |
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| `0x02` | note events | REQUIRED |
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### 2.1 Contract
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```json
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{ "channels": 1, "duration": 34000, "numeric": "wai.det.fixed64",
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"sample_rate": 22050 }
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```
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`duration` is the rendered mixdown length in samples.
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### 2.2 Notes
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`n_notes u32`, then per note (65 bytes):
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`start u64 | dur u64 | phase_inc i64 Fx | gain i64 Fx | waveform u8 |
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attack u64 | decay u64 | sustain i64 Fx | release u64`.
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`phase_inc` is the per-sample phase advance `freq / sample_rate`,
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authored off-line from the pitch — so the floor never evaluates an
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exponential to turn a note into a frequency (the same authoring
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discipline as the avatar quaternion). `waveform` selects a reference
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timbre: `0` saw, `1` square, `2` triangle, `3` 25%-pulse.
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## 3. Reference synthesis (trig-free)
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For each note, a phase accumulator advances by `phase_inc` each sample
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(wrapping at `1.0`); a **piecewise-linear** oscillator maps the phase to
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`[-1, 1]` (no trig); a **linear ADSR** envelope (attack ramp → decay to
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`sustain` → held until `dur` → release to zero over `release`) scales
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it; the result times `gain` accumulates into the mixdown buffer. Each
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output sample is quantized to `i16` (`round(v · 32767)`, half away from
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zero, clamped) in integer space. The whole path is `+ − × ÷` in the
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`Fx` floor — bit-identical on every machine.
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## 4. Conformance — mixdown-equivalence
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> Given the same `wai.audio.score`, a conforming sink MUST reconstruct
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> the identical canonical `i16` PCM via the reference synth, hence the
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> identical BLAKE3 — on every machine, no tolerance parameter.
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```
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mixdown_hash = BLAKE3("wai:score-mixdown\x01" || i16le PCM)
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score_hash = BLAKE3("wai:score\x01" || contract || notes) // identity
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```
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A sink MAY play a soundfont/neural instrument instead; that is
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presentation and does not affect conformance, exactly as the audio-scene
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HRTF render or the worlds renderer does not.
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## 5. Receipt (JWP profile)
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`score_hash` is the identity; the group's objects are the mix PCM blocks
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(per a fixed sample span), Merkle-bound; one Ed25519 signature over
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score_hash + root + exact work (= duration × notes) + carried
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`joules_micro`; `parent_receipt_hash` chains — the worlds/audio receipt
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shape reused.
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## Appendix
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Mixdown-equivalence is spatial audio's criterion with the recorded
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objects replaced by note events: both render a deterministic `i16` mix
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in the `Fx` floor and hash it. The score is the most extreme
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instructions-at-the-sink case in audio — there is no recording anywhere
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in the payload, only the composition. Sight, hearing, touch, motion,
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state, captured-content provenance — and now the composition itself —
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are one floor, one verification.
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