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AquaSynth/state/scratch.md
Meta Vens 82f99bc61d Approximate DX7 envelopes as ADSR
2026-05-13 16:55:30 +01:00

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Scratch

Current standing order: grow AquariumSynthCSharp through external reference targets, not through speculative field sprawl. state/spine.yaml and docs/reference-synth-roadmap.md are the handoff surfaces for agents working on the synth library while Aquarium work continues elsewhere.

Completed this slice:

  • Added Dx7EnvelopeApproximation, which lowers a DX7 four-rate/four-level EG to a labeled Aquarium ADSR approximation plus gate duration.
  • Reference rebuilds now record operator_envelope_approximation as matched pressure and operator_envelope_exactness as still missing.
  • Doctrine now states that DX7 EG approximation is not exact DX7 envelope execution.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 43 passed.

Previous slice:

  • Added field-site parameter binding for readable operator graph authoring: graph gain/note fields, operator ratio/level/feedback/envelope fields, and route index fields now accept @/param.
  • Operator graph Faust emission now substitutes bound parameter expressions at the exact /opgraphs/... field paths.
  • Fixed AD operator envelope binding to use /env/decay for the second AD value, matching the ADSR model instead of calling it release by accident.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 42 passed.

Previous slice:

  • Added a patch-level Playback contract for OneShot, Mono, and Poly playback with Faust MIDI polyphony settings.
  • instrument midi=true polyphony=8 now lowers to Faust's standard [midi:on][nvoices:8] option and freq, gain, gate controls.
  • Host/MIDI playback no longer emits per-voice /voices/0/note/frequency and /voices/0/note/gate controls; Faust architecture owns allocation.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 41 passed.

Previous slice:

  • Split note timing from envelope shape. Note now owns frequency, one-shot gate duration, and host/MIDI source; Envelope now owns ADSR shape: attack, decay, sustain level, and release.
  • SFXR sustain duration now maps to Note.GateSeconds; SFXR punch maps to a lower ADSR sustain level plus voice gain compensation during import/legacy parsing.
  • Added host note mode for MIDI-oriented patches through stable note frequency and note gate controls in generated Faust.
  • Moved built-in authoring examples off punch= and onto sustain_level=.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 40 passed.

Previous slice:

  • Replaced the DX7 algorithm-8 authoring surface with readable operator graph syntax: operator, route, and carrier declarations.
  • Added env=ad:attack:decay and env=adsr:attack:decay:sustain:release envelope forms for operator declarations.
  • Kept compact ops=/edges= syntax as parser/interchange scaffolding, but it is no longer the built-in authoring example.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 36 passed.

Previous slice:

  • Added a first-class OperatorGraph model with operators, modulation edges, carriers, graph gain, and operator feedback.
  • Added opgraph patch-script syntax. Example: opgraph name=core freq=330 carriers=1,3 ops=6:4:.9,5:3:.8,4:2:.7:.18,3:2:.6,2:1:.75,1:1:.82 edges=6>5:1.1,5>3:.9,4>3:.75,2>1:.85
  • Faust emission now mixes operator graphs alongside normal voices.
  • Updated the DX7 algorithm-8 rebuild to use a real operator graph for the topology. The remaining missing feature is exact DX7 feedback-register timing and DX7 rate/level envelopes, not graph ownership.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 35 passed.

Earlier rebuild slice:

  • Added ReferenceRebuild and ReferenceRebuildCatalog for explicit reference-target rebuild attempts.
  • Added two DX7-style Aquarium DSL rebuilds:
    • dx7/algo32-additive-organ: algorithm 32's six-carrier additive shape, which maps cleanly to six Aquarium voices.
    • dx7/algo8-bright-pair: algorithm 8's two-carrier FM shape, which is only an approximation because the current voice DSL cannot express 6->5, 4+5->3, 2->1, or operator-local self-feedback.
  • Added matched/missing feature records so topology mismatch becomes evidence instead of being hidden inside prose.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 34 passed.

Earlier topology slice:

  • Added DX7 algorithm topology metadata for algorithms 1-32 using Ken Shirriff's reverse-engineered OPS algorithm ROM table.
  • Dx7SysEx.AlgorithmTopology now exposes carrier operators, modulation edges, feedback-register writers, direct self-feedback operators, delayed-feedback targets, and raw ROM steps.
  • Dx7Voice.Features() now emits carrier_operators, modulation_edge_count, feedback_sources, and self_feedback_operators.
  • Representative tests cover algorithm 8, algorithm 16, and algorithm 32.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 31 passed.

Earlier slice:

  • Added Dx7SysEx records and parsing for DX7 voice edit buffers, packed 128-byte voices, and packed 32-voice SysEx banks.
  • Extracted six operators, envelopes, algorithm, feedback, oscillator sync, pitch envelope, LFO, transpose, and voice name into neutral DX7 records.
  • Added Dx7Voice.ToReferencePatch and structural feature extraction so DX7 voices can pressure the reference model before translation exists.
  • Checksum validation rejects bad wrapped SysEx payloads.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 28 passed.

Parameter slice:

  • Added explicit PatchParameter contracts: stable path, label, default, min, max, step, unit, automation-rate notes, and notes.
  • Added neutral ReferencePatch, ReferenceSource, and ReferenceFeature contracts with provenance/license/hash-ready fields.
  • Added param script declarations and duplicate parameter path validation.
  • Updated Faust emission so declared parameters produce smoothed hslider controls.
  • Implemented Option B parameter binding: numeric fields may reference declared parameters with @/path, for example lpf=@/macro/brightness. The parser records an exact field binding such as /voices/0/filter/lpf and keeps the parameter default as the graph value.
  • Faust emission substitutes the parameter expression only at the bound field site. Unbound parameters still emit a warning.
  • Verified with dotnet test AquariumSynthCSharp.slnx --no-restore: 23 passed.

Next likely slice:

  • Refine operator graphs with parameter bindings inside graph fields and decide how host MIDI note age/retrigger semantics should be represented beyond the current frequency/gate controls.
  • Keep tests focused on structure first, then add rendered audio comparison once the render path is explicit.