Proposal: Extended Pedal Tone Modules (Wah, Fuzz, Clean Boost)

[NickFlach]

Context

With the recent addition of distortion.h (PR #47), AudioNoise now has basic waveshaping for overdrive/distortion tones. This proposal extends the pedal library with additional modules that require different DSP approaches.

Proposed Modules

Module	Description	Key New Primitives Needed
Wah	Swept bandpass filter (manual or auto)	Envelope follower
Fuzz	Octave-up, gated, square-wave clip	Foldback distortion, noise gate integration
Clean Boost	Transparent gain + tone shaping	Existing biquads suffice
Bright Character	Presence/twang EQ	Peaking/shelving filters

New Primitives Required

envelope.h - For auto-wah and dynamics-controlled effects:

• envelope_follow(state, in, attack, release) - tracks signal amplitude

Extended waveshapers (complement existing distortion.h):

• fold_back(x, threshold) - signal folds back when exceeding threshold, creates complex harmonics for synth-fuzz tones
• tube_clip(x) - polynomial tube approximation with soft knee
• diode_clip(x, ratio) - asymmetric diode emulation

Implementation Approach

• Follow existing *_init(pot1-4) + *_step(in) pattern
• Self-contained headers with no assumed external dependencies
• Reference distortion.h for waveshaping patterns
• Integrate with existing noise gate work (commit 2a4f191)

Related

• Builds on PR Add distortion effect with soft/hard/asymmetric clipping modes #47 (distortion) - merged
• Complements Issue "Purring" bass guitar effects #18 (bass purr) explorations
• Follows design principles in pending PR Add CONTRIBUTING.md with contribution guidelines (includes DCO) #44 (CONTRIBUTING.md)

Happy to submit a PR starting with the extended waveshaper primitives.