# DeepPluck V0.2.0b Final Implementation Report

Date: 2026-08-29

Milestone: V0.2.0b First Musical Pluck

Specification: `Docs/DeepPluck_V0.2.0b_MasterPrompt_Rev2.txt`

## 1. Overall Result

**AUTOMATABLE IMPLEMENTATION COMPLETED**

The implementation, builds, automated tests, artifact checks, realtime review, and hidden Standalone startup smoke test are complete. Musical listening, visible GUI inspection, and Cubase host validation require the user environment and remain explicitly open under **MANUAL VERIFICATION REQUIRED**. The milestone must not be called musically accepted until those checks pass.

## 2. Starting Point

- Branch: `master`
- Confirmed starting commit: `e1314ab DeepPluck V0.2.0a Audio Engine Foundation`
- Existing user work protected: modified `AGENTS.md`; untracked `Docs/` and `CubaseTest/`
- Baseline Debug and Release builds succeeded.
- All seven baseline CTest suites passed in Debug and Release before implementation.

## 3. Files

Created:

- `Source/Presets/DeepPluckPresets.h`
- `Source/Presets/DeepPluckPresets.cpp`
- `Docs/DeepPluck_V0.2.0b_Implementation_Report.md`

Modified:

- `CMakeLists.txt`
- `Source/Parameters/DeepPluckParameters.h/.cpp`
- `Source/Synth/DeepPluckOscillator.h/.cpp`
- `Source/Synth/DeepPluckEnvelope.h/.cpp`
- `Source/Synth/DeepPluckVoice.h/.cpp`
- `Source/Synth/DeepPluckSynthesiser.cpp`
- `Source/PluginEditor.h/.cpp`
- `Tests/TestMain.cpp`
- `README.md`
- `ARCHITECTURE.md`

No file inside `JUCE/` was changed. No system plugin installation occurred.

## 4. Architecture

The V0.2.0a processor/synthesiser/voice ownership remains intact. The milestone replaces the JUCE ADSR wrapper with a project-owned `DeepPluckEnvelope` state machine and adds a small immutable preset module. The processor still takes one bounded six-parameter snapshot per block; voices read that snapshot and update envelope coefficients only when a value or stage changes.

The signal flow remains:

`PolyBLEP Saw -> DeepPluckEnvelope -> Velocity -> Voice Gain -> Voice Sum -> Smoothed Output Gain`

The editor owns no DSP. Preset application and matching stay on the message thread.

## 5. DSP and Musical Benefit

### PolyBLEP saw

The naive saw wrap is corrected with PolyBLEP using phase before advance. Frequency changes preserve phase; invalid/nonpositive frequency produces silence. The implementation is table-free, non-oversampled, bounded, and allocation-free.

Measured deterministic test metric:

- PolyBLEP/non-harmonic-energy ratio versus naive saw: **0.0286427**

The automated spectral case therefore retains about 2.86% of the naive test's non-harmonic alias energy.

### Live DeepPluckEnvelope

Stages are idle, Attack, Decay, Sustain, and Release. Target-ratio recurrences use 0.30 for Attack and 0.0001 for Decay/Release. Sustain moves over a fixed 15 ms safety ramp.

Live Attack/Decay/Sustain/Release changes reconfigure only the remaining curve from the current value. They do not restart a stage or jump the level. Release shortening and extension act on voices already in Release.

### Immediate Note-Off

Note-Off transitions Attack, Decay, or Sustain directly to Release at the current level. Regression tests prove that an early Decay Note-Off finishes on Release time rather than completing the remaining Decay first.

### Musical voice stealing

The fixed 16-voice engine chooses a free voice, then the quietest released voice, then the quietest remaining voice. Equal-level ties select the oldest candidate. Unavoidable hard steals retain and fade the previous output sample for two milliseconds while the new note begins immediately.

### Gain staging

- Voice gain: 0.08
- Default Output: -3 dB
- Output smoothing: 20 ms after the full voice sum
- Measured automated default 16-voice peak: **0.548785**
- Acceptance limit: 0.95

No limiter, compressor, soft clipper, active-voice normalization, or hidden auto-gain was added.

## 6. Sound Manifest

The implementation supports the Sound Manifest through reduced high-note digital harshness, expressive live envelopes, preserved velocity dynamics, conservative headroom, musical voice selection, a calm focused GUI addition, and dry factory starting points. It does not add unrelated synthesis or effects.

**Does this make DeepPluck a better instrument for emotional Deep House plucks?**

Yes at the implementation-contract level: the source is cleaner, the envelope reacts like an instrument instead of a frozen snapshot, note release follows the player immediately, and defaults/presets are focused on pluck use. The remaining filterless saw is intentionally brighter than the complete long-term Sound Manifest target; musical listening must confirm the subjective result.

## 7. Parameters, State, and Presets

The six persistent IDs and ranges are unchanged. New defaults are:

- Output -3 dB
- Master Tune 440 Hz
- Attack 0.003 s
- Decay 0.320 s
- Sustain 0
- Release 0.180 s

Factory presets:

- Deep Pluck
- Soft Pluck
- Tight Pluck
- Long Pluck

Deep Pluck exactly matches the APVTS defaults. Nonmatching values display Custom. V0.1 migration and all-six-value state roundtrip tests pass; V0.2.0a values are overlaid without replacement by new defaults.

## 8. Realtime Review

Reviewed hot paths:

- processor block snapshot/render/output smoothing
- sample-accurate MIDI dispatch
- voice selection and rendering
- PolyBLEP processing
- envelope sample recurrence and live coefficient updates

No audio-path heap allocation, container growth, mutex, blocking call, file/network access, logging, string construction, GUI access, or APVTS string lookup was introduced. `exp`/`log` occur only at stage/configuration changes, never per sample. All scans are bounded by 16 voices.

## 9. Builds and Artifacts

Environment detected:

- MSVC 19.51.36256.0
- Windows SDK 10.0.26100.0
- CMake generator Visual Studio 18 2026, x64
- local JUCE 9

Final Debug and Release builds succeeded without new compiler or linker warnings. Produced and verified:

- `Artifacts/Debug/DeepPluck.vst3`
- `Artifacts/Debug/DeepPluck.exe`
- `Artifacts/Release/DeepPluck.vst3`
- `Artifacts/Release/DeepPluck.exe`

Release VST3 module metadata reports ToneTrax, Instrument/Synth, and version 0.2.0. The Release Standalone started and stayed alive for the three-second hidden smoke interval, then was intentionally terminated.

## 10. Automated Tests

Final Debug: **7/7 passed**

Final Release: **7/7 passed**

Coverage includes:

- parameter IDs/ranges/defaults, preset matching/application, state migration/roundtrip
- oscillator safety, pitch, phase continuity, and PolyBLEP alias-energy comparison
- envelope bounds, timing, immediate Attack/Decay-to-Release, continuity, and live ADSR changes
- live Release shortening/extension at envelope and rendered-voice integration level
- musical voice stealing, fixed voice count, retained fade, velocity, and lifecycle
- sample-accurate note events
- 44.1/48/96 kHz with block sizes 1/32/64/127/512
- output/tune/sustain smoothing, default 16-voice headroom, and stress stability

No test was disabled or removed.

## 11. Listening Acceptance

**MANUAL VERIFICATION REQUIRED**

Required manual checks remain:

- Default sound is warm, soft, focused, expressive, and immediately playable.
- High notes are audibly less scratchy/alias-like than V0.2.0a without pitch loss.
- Attack, Decay, Sustain, and Release automation remains click-free.
- Note-Off during Attack and Decay starts Release immediately by ear.
- Release 5 s -> 0.05 s and 0.05 s -> 5 s during active tails is natural and click-free.
- 2/4/8/16/17-note playing remains balanced; stealing is unobtrusive.
- All four dry presets are useful and clearly distinguishable.
- Five-minute mixed-performance stability test.

## 12. Cubase Validation

**MANUAL VERIFICATION REQUIRED**

Cubase installation was deliberately not automated. Required groups:

- current VST3 discovery, load/unload, editor open/close and visual layout
- MIDI, repeated notes, chords, sustain pedal, All Notes Off, stop/start
- all live-envelope edge cases, especially Note-Off during Decay and active-tail Release changes
- Write/Read and supported Touch/Latch automation for all six parameters
- preset/Custom behavior, Undo/Redo, current and old project recall
- buffer sizes 64/128/256/512, realtime/offline bounce, mono/stereo, multiple instances
- subjective Sound Manifest and factory-headroom acceptance

## 13. Headroom and Performance

The deterministic factory-headroom test passes at 0.548785 peak for the defined 16-voice render, below 0.95. CPU behavior remains bounded and allocation-free. A full reproducible performance benchmark is intentionally deferred until filter/unison/effects provide a meaningful comparison basis.

## 14. Regression Review

Permanent automated regressions now cover:

- Note-Off during Attack must enter Release immediately.
- Note-Off during Decay must enter Release immediately.
- A released voice must react to shorter and longer live Release values.
- Active Sustain changes must smooth instead of jump.
- PolyBLEP must retain a substantial alias-energy advantage over the naive saw.
- Quiet released voices are preferred for stealing.
- Default 16-voice output remains below the factory peak gate.

All previous parameter, state, sample-accuracy, matrix, smoothing, and lifecycle suites still pass.

## 15. Known Limitations and Technical Debt

- PolyBLEP reduces but does not eliminate aliasing.
- The filterless source cannot yet achieve the complete soft/rounded tonal target.
- The four presets are internal development presets, not a full preset browser/bank.
- GUI appearance and interaction need visible manual inspection.
- Cubase, audio-device, listening, offline-bounce, and multiple-instance validation remain manual.
- CPU benchmark infrastructure remains deliberately deferred.

No known code defect is being hidden as a future feature.

## 16. Git

Focused implementation commit:

- `e2bc67f DeepPluck V0.2.0b First Musical Pluck`

This report update is necessarily recorded after that implementation commit so the hash can be stated without a self-referential commit. `CubaseTest/` and the unrelated historical Rev1 prompt files remain untracked and were not staged automatically.

## 17. Design Review

**Did the implementation improve musical quality?**

Expected yes: alias reduction, live envelopes, immediate Note-Off, musical stealing, and conservative defaults all target audible/playable behavior. Final subjective confirmation requires listening.

**Did complexity increase, and was it justified?**

Yes, in the envelope state machine, preset module, and click-safe steal tail. Each addition implements a named musical contract and remains bounded/tested.

**Does it follow the Sound Manifest?**

Yes by design: dry quality, dynamics, headroom, focus, calm UI growth, and musical usefulness were prioritized over feature count.

**Would a musician immediately hear or feel the improvement?**

The cleaner high register and responsive release behavior should be immediate. This remains a manual listening acceptance question, not an automated claim.

**Keep, refactor, or revert?**

Keep pending manual musical/Cubase acceptance. The implementation has complete automated coverage and no identified architectural regression.

## 18. Next Milestone Recommendation

Implement one focused musical filter plus filter envelope. It is the most direct next step toward the Sound Manifest's soft, rounded, controlled tonal identity. Do not start oscillator 2, unison, or effects in the same milestone.
