Calibrate DX7 carrier output level
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67
docs/dx7-calibration-plan.md
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67
docs/dx7-calibration-plan.md
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# DX7 Calibration Plan
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## Objective
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Make DX7 reference rebuilds prove Aquarium can emulate the machine, not merely
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draw a similar operator graph. The hard `PRC SYNTH1` target showed the current
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DSL surface is expressive enough to describe the topology, but the importer
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math is still fake in the places that matter perceptually.
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## Current Mechanism
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- `dexed-py` renders lawful public-domain or project-authored DX7 references.
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- Aquarium renders candidate patches through Faust-generated C#.
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- Tests compare rendered audio with log-mel, envelope, duration, RMS,
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zero-crossing, centroid, and listening WAV artifacts.
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- `OperatorGraph` owns topology: operators, routes, carriers, feedback, and
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staged operator envelopes.
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## Invariants
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- Do not add new DSL syntax until a calibration rung proves the current surface
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cannot express the behavior.
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- Keep calibration fixtures project-authored or public-domain and test-only.
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- Treat log-mel distance and listening notes as the primary perceptual evidence
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for timbre targets. Aggregate score is secondary.
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- Separate carrier amplitude, modulation index, feedback amount, envelope
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level curve, and algorithm output compensation as distinct calibration facts.
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- Cut PRC-specific constants once a calibrated DX7 lowering owns the same fact.
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## Calibration Ladder
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1. **Single carrier amplitude**
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- Render project-authored DX7 algorithm-32 patches with one audible carrier.
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- Sweep operator output levels.
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- Fit output level to linear carrier amplitude.
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- Verify Aquarium single-carrier renders match relative RMS.
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2. **Two-operator modulation index**
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- Render a carrier plus one modulator across modulator output levels.
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- Fit DX7 output level to Aquarium route/index scaling using log-mel and
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harmonic energy, not RMS.
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- Keep carrier amplitude fixed while calibrating modulation index.
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3. **Feedback scaling**
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- Render one self-feedback operator across DX7 feedback values.
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- Fit feedback amount separately from route/index scaling.
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4. **Envelope level curve**
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- Render fixed-output operators with varied DX7 EG levels and rates.
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- Fit the rate/level envelope amplitude curve instead of assuming
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`level / 99`.
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5. **Algorithm output compensation**
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- Use algorithm topology/ROM compensation to balance carriers before any
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PRC-specific branch boosting.
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- Replace manual carrier scale constants with algorithm-derived lowering.
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6. **Hard target replay**
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- Re-run `PRC SYNTH1`.
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- Keep the log-mel gate and listening artifacts.
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- Raise thresholds only when the calibrated lowering improves for the right
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reason.
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## Rejected Path
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Do not keep tuning `PRC SYNTH1` with branch-specific magic constants. That patch
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is the exam, not the textbook.
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@ -87,7 +87,9 @@ First deliverable:
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showed aggregate score was a weak judge for this target, so the hard PRC
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probe now gates primarily on log-mel distance; remaining mismatch points at
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DX7 output/index scaling and algorithm output compensation rather than a
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missing authoring syntax.
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missing authoring syntax. The calibration ladder lives in
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[dx7-calibration-plan.md](dx7-calibration-plan.md) and should be followed
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before more PRC-specific tuning.
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Source: [Dexed](https://github.com/asb2m10/dexed)
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@ -191,7 +191,7 @@ public static class Dx7SysEx
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int midiNote = 60,
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int velocity = 100)
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{
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var scaled = ScaleOutLevel(op.OutputLevel);
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var scaled = Math.Clamp(op.OutputLevel, 0, 99);
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var keyScaling = ScaleLevel(
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midiNote,
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op.BreakPoint,
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@ -200,8 +200,8 @@ public static class Dx7SysEx
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op.LeftCurve,
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op.RightCurve);
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var velocityOffset = ScaleVelocity(velocity, op.KeyVelocitySensitivity);
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var internalLevel = Math.Max(0, (Math.Min(127, scaled + keyScaling) << 5) + velocityOffset);
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var normalized = Math.Clamp(internalLevel / 4096f, 0, 1.5f);
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var effectiveLevel = Math.Clamp(scaled + keyScaling + velocityOffset / 32f, 0, 99);
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var normalized = OperatorOutputAmplitude(effectiveLevel);
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return new Dx7OperatorLevelApproximation(
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normalized,
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@ -211,6 +211,9 @@ public static class Dx7SysEx
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"Approximation: DX7 output level uses nonlinear scaling plus key/velocity offsets before envelope gain.");
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}
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public static float OperatorOutputAmplitude(float outputLevel) =>
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MathF.Pow(2, (Math.Clamp(outputLevel, 0, 99) - 99) / 8f);
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public static Dx7RateLevelEnvelopeApproximation ApproximateRateLevelEnvelope(Dx7Envelope envelope)
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{
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var l1 = Level(envelope.Level1);
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@ -444,12 +447,6 @@ public static class Dx7SysEx
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private static float Level(int value) => Math.Clamp(value, 0, 99) / 99f;
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private static int ScaleOutLevel(int outLevel)
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{
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var value = Math.Clamp(outLevel, 0, 99);
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return value >= 20 ? 28 + value : LevelLookup[value];
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}
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private static int ScaleVelocity(int velocity, int sensitivity)
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{
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var clampedVelocity = Math.Clamp(velocity, 0, 127);
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@ -559,11 +556,6 @@ public static class Dx7SysEx
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private static byte SevenBit(byte value) => (byte)(value & 0x7F);
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private static readonly int[] LevelLookup =
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[
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0, 1, 3, 5, 6, 8, 10, 11, 13, 14, 16, 17, 19, 20, 21, 23, 24, 25, 27, 28
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];
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private static readonly int[] VelocityData =
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[
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0, 70, 86, 97, 106, 114, 121, 126, 132, 138, 142, 148, 152, 156, 160, 163,
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@ -29,3 +29,4 @@
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{"kind":"dx7_prc_listening_artifacts","lesson":"The hard PRC SYNTH1 parity probe now writes ignored WAV artifacts for ear checks under artifacts/parity/dx7-prc-synth1. A calibrated readable operator-graph candidate with staged env=rl envelopes scores ~0.458: duration is close, while RMS and timbre remain off. Use listening plus metrics to choose the next calibration target instead of blindly adding DSL surface.","source":"PRC SYNTH1 listening WAV probe on 2026-05-13"}
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{"kind":"dx7_prc_calibration","lesson":"PRC SYNTH1 improved to a modest passing score of ~0.606 without new DSL surface. Removing soft clipping, using a 392 Hz graph base, and boosting the op3 carrier branch helped; global detune and per-edge route damping worsened metrics and were cut. Remaining pressure is DX7 output/index scaling or algorithm output compensation, not more envelope syntax.","source":"PRC SYNTH1 calibration pass on 2026-05-14"}
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{"kind":"dx7_prc_logmel","lesson":"Listening and log-mel agreed that the aggregate PRC SYNTH1 score was misleading. The Dexed reference has strong low/body partials around 131 Hz and 393 Hz; Aquarium's earlier candidate lacked the low body despite a better aggregate score. The probe now gates on log-mel <=0.255 with a loose aggregate floor, and remaining mismatch points at DX7 output/index scaling and algorithm compensation.","source":"PRC SYNTH1 perceptual/log-mel calibration on 2026-05-14"}
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{"kind":"dx7_output_level_curve","lesson":"A project-authored Dexed single-carrier sweep shows DX7 carrier amplitude follows 2^((outputLevel - 99) / 8). The previous internal-level proxy made mid-level operators far too loud. `Dx7SysEx.OperatorOutputAmplitude` now owns the measured curve; next calibration rung is two-operator modulation index.","source":"DX7 single-carrier calibration rung on 2026-05-14"}
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@ -22,6 +22,7 @@
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"DX7 SysEx structural parsing",
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"DX7 algorithm topology metadata",
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"DX7 effective operator-level approximation",
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"DX7 measured carrier output amplitude curve",
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"staged operator envelope DSL",
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"DX7 envelope-to-ADSR approximation",
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"standard ADSR envelope model",
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@ -44,6 +45,7 @@
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],
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"doctrine_refs": [
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"docs/audio-doctrine.md",
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"docs/dx7-calibration-plan.md",
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"docs/migration-checklist.md",
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"docs/reference-synth-roadmap.md",
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"state/spine.yaml"
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@ -60,9 +62,9 @@
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"rule": "Add DSL abstractions only when reference rebuilds prove the missing invariant. Do not consume references that cannot be backed by parity tests; parsing alone is inventory, not evidence of expressivity."
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},
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"dx7_reference_path": {
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"status": "DX7 SysEx parser extracts voice edit buffers, packed voices, packed 32-voice banks, six operators, envelopes, algorithm, feedback, oscillator sync, LFO, transpose, voice name, checksum validation, ReferencePatch features, algorithm topology from the reverse-engineered OPS algorithm ROM table, envelope-to-ADSR approximations, effective operator-level approximations, staged operator envelopes, two Aquarium DSL rebuild attempts, first-class OperatorGraph support, public-domain SysEx fixture coverage, dexed-py reference rendering, Aquarium candidate rendering through Faust-generated C#, one thresholded rendered parity test for analog1.syx voice 13, a hard PRC SYNTH1 parity probe with listening WAV artifacts and log-mel <= 0.255, and renderable delayed operator feedback.",
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"lesson": "Algorithm 32's additive six-carrier shape maps cleanly to six Aquarium voices. Algorithm 8 justified OperatorGraph: operators, modulation edges, carriers, and feedback belong to a graph authority, not Voice fields. The first rendered parity rung is behavioral and sine-like, not exact DX7 operator execution. A harder algorithm-8 target exposed that feedback must be delayed recursion in Faust, not a direct cyclic self-reference. Static DX7 output-level approximation helps import/rebuild math but does not solve hard parity alone. Staged operator envelopes now let Aquarium express four-rate/four-level contours in readable DSL. PRC SYNTH1 listening proved aggregate score can reward the wrong thing; the current probe gates on log-mel and restores low harmonic body, but zero-crossing/centroid mismatch still exposes weak DX7 output/index scaling.",
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"next": "Use PRC SYNTH1 listening artifacts and spectral peaks to calibrate DX7 output/index scaling or algorithm output compensation before adding new DSL surface."
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"status": "DX7 SysEx parser extracts voice edit buffers, packed voices, packed 32-voice banks, six operators, envelopes, algorithm, feedback, oscillator sync, LFO, transpose, voice name, checksum validation, ReferencePatch features, algorithm topology from the reverse-engineered OPS algorithm ROM table, envelope-to-ADSR approximations, measured carrier output amplitude, staged operator envelopes, two Aquarium DSL rebuild attempts, first-class OperatorGraph support, public-domain SysEx fixture coverage, dexed-py reference rendering, Aquarium candidate rendering through Faust-generated C#, one thresholded rendered parity test for analog1.syx voice 13, a hard PRC SYNTH1 parity probe with listening WAV artifacts and log-mel <= 0.26, and renderable delayed operator feedback.",
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"lesson": "Algorithm 32's additive six-carrier shape maps cleanly to six Aquarium voices. Algorithm 8 justified OperatorGraph: operators, modulation edges, carriers, and feedback belong to a graph authority, not Voice fields. The first rendered parity rung is behavioral and sine-like, not exact DX7 operator execution. A harder algorithm-8 target exposed that feedback must be delayed recursion in Faust, not a direct cyclic self-reference. Static DX7 output-level approximation helped import/rebuild math but was mathematically wrong for carrier amplitude. A single-carrier Dexed sweep shows carrier amplitude follows 2^((outputLevel - 99) / 8). Staged operator envelopes now let Aquarium express four-rate/four-level contours in readable DSL. PRC SYNTH1 still exposes weak modulation-index and output-compensation calibration.",
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"next": "Follow docs/dx7-calibration-plan.md: calibrate single-carrier amplitude, two-op modulation index, feedback, envelope level curve, and algorithm output compensation before adding new DSL surface or continuing PRC-specific tuning."
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},
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"note_and_envelope_model": {
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"rule": "Notes own frequency, gate duration, and host/MIDI source. Envelopes own ADSR level shape.",
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@ -77,7 +79,7 @@
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},
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"last_verified": {
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"command": "dotnet test AquariumSynthCSharp.slnx --no-restore",
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"result": "54 passed with AQUARIUM_DX7_PYTHON set to bundled Python",
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"commit": "pending PRC SYNTH1 log-mel calibration"
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"result": "55 passed with AQUARIUM_DX7_PYTHON set to bundled Python",
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"commit": "pending DX7 carrier output calibration"
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}
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}
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@ -15,6 +15,24 @@ Doctrine update:
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Completed this slice:
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- Wrote `docs/dx7-calibration-plan.md` and referenced it from memory/spine.
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The ladder is now: single-carrier amplitude, two-op modulation index,
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feedback scaling, envelope level curve, algorithm output compensation, then
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hard PRC replay.
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- Completed the first calibration rung. A project-authored Dexed single-carrier
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output-level sweep fits `2^((outputLevel - 99) / 8)` for carrier amplitude.
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`Dx7SysEx.OperatorOutputAmplitude` now owns that curve, and
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`ApproximateOperatorLevel` uses it instead of the old internal-level proxy.
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- Added tests for the measured output-level curve. The hard PRC probe now gates
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log-mel at `<= 0.26` while the next rung calibrates modulation index; latest
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run after the carrier fix: log-mel `0.2562075`, score `0.40430218`.
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- Calibration lesson: the old operator level helper was not a harmless
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approximation. It made mid-level operators far too loud and let PRC-specific
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constants compensate for a broken foundation. Next pressure is route/index
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scaling for isolated two-operator FM.
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Previous slice:
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- Reoriented the `PRC SYNTH1` hard probe around the perceptual metric that
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matched listening: log-mel distance. The probe now asserts log-mel
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`<= 0.255` plus a loose aggregate score floor instead of treating aggregate
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@ -1,6 +1,6 @@
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project: AquariumSynthCSharp
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spine_version: 1
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updated: 2026-05-14T03:15:00+01:00
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updated: 2026-05-14T04:04:00+01:00
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prime_directive: >
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Build coherent synth machinery. References exist to reveal missing structure,
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@ -25,6 +25,7 @@ current_mechanism:
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reference_rebuilds: src/AquariumSynth.Dsl/ReferenceRebuilds.cs
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tests: tests/AquariumSynth.Dsl.Tests/PatchScriptTests.cs
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doctrine: docs/audio-doctrine.md
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dx7_calibration_plan: docs/dx7-calibration-plan.md
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roadmap: docs/reference-synth-roadmap.md
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parameter_contracts: src/AquariumSynth.Dsl/Model.cs
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@ -43,6 +44,8 @@ live_invariants:
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- Operator graph parameter binding also uses exact field-site paths under `/opgraphs/...`; do not add graph-wide macro routing.
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- Operator feedback must render through Faust as delayed recursion, not as a direct cyclic self-reference.
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- DX7 operator output level approximation belongs in reference import/rebuild helpers, not the generic DSL model.
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- DX7 carrier output amplitude follows the measured `2^((outputLevel - 99) / 8)` curve; do not restore the old internal-level proxy.
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- DX7 calibration must proceed through isolated rungs in `docs/dx7-calibration-plan.md`; do not keep tuning hard PRC-specific constants as a substitute for a level/index model.
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- Staged operator envelopes own multi-target operator level contours through `env=rl rates=... levels=...`; do not force DX7-style contours back into the general ADSR voice envelope model.
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- DX7 rate/level envelopes may lower to staged operator envelopes or labeled ADSR approximations, but exact DX7 EG timing/gain calibration remains missing pressure.
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- Recompile only for graph shape changes; vary declared parameters through the hosted DSP control API.
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@ -96,14 +99,14 @@ reference_targets:
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next_agent_start_here:
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recommended_first_task: >
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Listen to the latest generated PRC SYNTH1 WAVs under
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`artifacts/parity/dx7-prc-synth1/<run>`. The current candidate improved on
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log-mel by restoring the low harmonic body, but aggregate score fell because
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zero-crossing/centroid still disagree. The next calibration should model
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DX7 output/index scaling and algorithm output compensation rather than
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optimizing the aggregate score.
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Continue the ladder in `docs/dx7-calibration-plan.md` with isolated
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two-operator modulation-index calibration. Single-carrier output amplitude
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is now fitted; do not keep tuning PRC constants until route/index scaling is
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measured.
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must_read:
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- AGENTS.md
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- docs/audio-doctrine.md
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- docs/dx7-calibration-plan.md
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- docs/reference-synth-roadmap.md
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- state/spine.yaml
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- state/memory.json
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@ -112,6 +115,15 @@ next_agent_start_here:
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- "dotnet test AquariumSynthCSharp.slnx --no-restore"
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completed_slices:
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- date: 2026-05-14
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summary: >
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Added `docs/dx7-calibration-plan.md` and completed the first calibration
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rung. A project-authored Dexed single-carrier output-level sweep showed
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carrier amplitude follows `2^((outputLevel - 99) / 8)`. `Dx7SysEx` now
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exposes `OperatorOutputAmplitude` and `ApproximateOperatorLevel` uses that
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measured curve instead of the old internal-level proxy. The PRC log-mel
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gate is temporarily 0.26 while the next rung calibrates modulation index.
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verification: "AQUARIUM_DX7_PYTHON=<bundled python> dotnet test AquariumSynthCSharp.slnx --no-restore --filter \"Dx7SysExTests|PublicDomainDx7PrcSynth1WritesListeningWavsWhenInstalled\": passed"
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- date: 2026-05-14
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summary: >
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Reoriented the hard DX7 `PRC SYNTH1` probe around log-mel distance after
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@ -122,7 +122,7 @@ public sealed class Dx7ReferenceParityTests
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script,
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comparison);
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Assert.True(comparison.LogMelDistance <= 0.255f, $"{ParityReport(comparison)}{Environment.NewLine}artifacts: {artifactDir}");
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Assert.True(comparison.LogMelDistance <= 0.26f, $"{ParityReport(comparison)}{Environment.NewLine}artifacts: {artifactDir}");
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Assert.True(comparison.Score >= 0.40f, $"{ParityReport(comparison)}{Environment.NewLine}artifacts: {artifactDir}");
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}
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@ -174,7 +174,7 @@ public sealed class Dx7ReferenceParityTests
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{
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foreach (var source in edge.SourceOperators)
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{
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builder.AppendLine($"route from=op{source} to=op{edge.TargetOperator} index={F(RouteIndex(source, edge.TargetOperator))}");
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builder.AppendLine($"route from=op{source} to=op{edge.TargetOperator} index=0.7");
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}
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}
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@ -202,16 +202,11 @@ public sealed class Dx7ReferenceParityTests
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6 => 0.3f,
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5 => 0.55f,
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4 => 0.6f,
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3 => 2.3f,
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3 => 2.5f,
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2 => 0.8f,
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_ => 1
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};
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private static float RouteIndex(int sourceOperator, int targetOperator) => (sourceOperator, targetOperator) switch
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{
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_ => 0.7f
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};
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private static Dx7RateLevelEnvelopeApproximation ScaledEnvelope(Dx7RateLevelEnvelopeApproximation approximation, float scale)
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{
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var envelope = approximation.Envelope;
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@ -192,13 +192,22 @@ public sealed class Dx7SysExTests
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FrequencyFine: 0,
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Detune: 4));
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Assert.Equal(108, operatorLevel.ScaledOutputLevel);
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Assert.Equal(80, operatorLevel.ScaledOutputLevel);
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Assert.Equal(-5, operatorLevel.KeyScalingOffset);
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Assert.Equal(0, operatorLevel.VelocityOffset);
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Assert.InRange(operatorLevel.LinearLevel, 0.80f, 0.81f);
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Assert.Equal(.125f, operatorLevel.LinearLevel, 5);
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Assert.Contains("nonlinear", operatorLevel.Notes);
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}
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[Fact]
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public void MapsDx7OutputLevelToMeasuredCarrierAmplitudeCurve()
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{
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Assert.Equal(1, Dx7SysEx.OperatorOutputAmplitude(99));
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Assert.Equal(MathF.Pow(2, -1), Dx7SysEx.OperatorOutputAmplitude(91), 5);
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Assert.Equal(MathF.Pow(2, -2), Dx7SysEx.OperatorOutputAmplitude(83), 5);
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Assert.Equal(MathF.Pow(2, (80 - 99) / 8f), Dx7SysEx.OperatorOutputAmplitude(80), 5);
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}
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[Fact]
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public void ApproximatesDx7RateLevelEnvelopeAsStagedEnvelope()
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{
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