Feature request: add Fuzz plugin for Pedalboard (#402)

[LorenzoMonti]

Problem

Fuzz is a staple effect in many music genres, particularly rock and
experimental electronic music. While distortion and gain effects exist
in Pedalboard, fuzz has a unique aggressive character that cannot be
easily replicated. Adding a fuzz plugin would expand Pedalboard’s
flexibility, providing more options for guitarists and producers
seeking vintage or experimental tones.

This feature request was initially discussed in #402.

Solution

Implemented a new Fuzz effect, emulating a classic fuzz pedal.
The effect consists of:

• A two-stage clipping process:
  • Hard diode clipping with a threshold of 0.25.
  • Soft clipping using a tanh function.
• A tone control stage, implemented as a low-pass filter.
• Unit tests verifying expected behavior.

Result

Pedalboard now includes a fuzz effect, broadening its range of
distortion-based effects. Users can apply fuzz to their audio chains
for a distinctive saturated sound characteristic of classic fuzz pedals.

[psobot]

Excellent work, thank you @LorenzoMonti! I've left a couple comments inline (mostly about touching the actual DSP parameters directly in the setters/getters rather than copies) - but otherwise, this is virtually a perfect pull request. Great job!

[psobot]

We probably don't want to keep a copy of these variables here, as they can differ from the variables set in the ProcessorChain depending on when prepare is called. (And indeed; if you use Fuzz in an AudioStream, it should be possible to call .drive_db = x and the audio should update without needing to stop and start the stream again.)

[psobot]

Suggested change

	void setDriveDecibels(const float f) noexcept { driveDecibels = f; }
	float getDriveDecibels() const noexcept { return driveDecibels; }
	void setDriveDecibels(const float f) noexcept { this->getDSP().template get<gainIndex>().setGainDecibels(f); }
	float getDriveDecibels() const noexcept { return this->getDSP().template get<gainIndex>().getGainDecibels(f); }

[psobot]

Could try using ArrayCoefficients here to allow updating the toneHz parameter without requiring a realloc/extra prepare call here - with the caveat that I haven't worked with that API in a long time and am not sure if it would actually work here.

[LorenzoMonti]

Excellent work, thank you @LorenzoMonti! I've left a couple comments inline (mostly about touching the actual DSP parameters directly in the setters/getters rather than copies) - but otherwise, this is virtually a perfect pull request. Great job!

Thanks for the thorough and speedy comment! I’m still getting familiar with JUCE, so I really appreciate the guidance. I’ll go through your comments carefully and deepen my understanding of how the ProcessorChain works.

[LorenzoMonti]

Dear @psobot,

Below are the changes I made to the Fuzz.h file:

• Parameter Storage Refactoring: replaced driveDecibels and toneHz with cached values currentDriveDecibels and currentToneHz. Morover I added currentSampleRate to store sample rate for filter updates.
• Parameter Getters and Setters: modified setDriveDecibels() to update both cached value and DSP chain and updated getDriveDecibels() to return cached value for const-correctness. Modified setToneHz() to update cached value and filter coefficients immediately, lastly kept getToneHz() returning cached value.
• Added helper methods updateDSPParameters() and updateFilterCoefficients() for centralized DSP parameter management.
• Improved filter coefficient handling for real-time tone parameter changes.

Let me know what you think about it.