bass-foundry/docs/patina

Patina

Patina smooths a sound’s rough surface without erasing its character. Formerly Resonance Compressor; current version 0.5.0.

A mixing effect that finds harsh, ringing regions as they happen and pulls them down, while plain harmonic tone passes. Independently designed in Rust; no claim of matching Soothe or Quance.

Install on Windows

Download the Windows artifact from the Gitea plugin's Gitea release, or the branch pipeline's windows job and extract the ZIP. Copy Patina.clap into C:\Program Files\Common Files\CLAP\. In FL Studio 2024.1 or newer, open Options → Manage plugins, enable Verify plugins, and Find installed plugins. Load Patina in a mixer effect slot. Keep the font license with redistributed packages.

Work with it

Each band works like a small compressor. It compares its level with the local floor around it and cuts only the part that sticks out:

• Depth is the largest cut per band, in dB. 0 dB does nothing.
• Sharpness sets what counts as a resonance. Low values follow broad, smooth bumps (honk, boxiness). High values target narrow rings and whistles.
• Threshold is how far (dB) a band must rise above its neighbours before it is cut. Low values treat any bump; high values treat only the worst.
• Ratio is how hard a bump above the threshold is cut. At n:1 a bump ends 1/n as far above the threshold as it started. Low ratios leave small bumps nearly alone and still cut big ones; ∞:1 flattens every bump to the threshold (this is how Patina worked before 0.5).
• Knee: Soft fades cuts in around the threshold. Hard starts them right at the threshold and uses half the Attack time.

The small graph under the knobs shows the result: bump height above the floor in, cut out, with the threshold and the Depth limit.

Start with Depth around 6 dB. Raise Threshold until only the harsh parts show cuts, then use Delta to hear what is removed. To hit big resonances hard and leave small ones alone, raise Depth to 12–20 dB and set Ratio to 2:1–4:1. Restrict Low/High frequency to keep the source’s body out of reach. Attack and Release set how quickly cuts grow and recover; Transient guard briefly relaxes cuts on attacks to keep punch.

Tone guard for bass lines

On a bass line, a bump can mean two things. A resonance fixed in Hz (a formant, a comb or filter ring) stays at the same frequency on every note: that is what Patina should cut. A bump that follows the note (a harmonic the patch is built on, or a Lathe boost) moves with every note: cutting it changes the patch differently on each note.

Tone guard tells them apart. Patina detects the played note (30–500 Hz) and remembers, over about four seconds, how high each bump was in Hz and how high it was relative to the note. A bump that has stayed with the note more than in Hz gets less cut; at 100 % none. A resonance fixed in Hz is cut as before. It needs a few different notes before it can decide: on one held note both look the same and Patina cuts as normal. The NOTE readout shows what Patina follows, and a blue strip on top of the plot shows where cuts are held back. Start from the Bass line preset. At 0 % Tone guard is off.

Measured on a saw line F1–F2 with Low at 150 Hz: a +12 dB boost on harmonic 6 is cut by 5.8 dB without Tone guard and by 0.4 dB at 100 %; a formant at 1.5 kHz is cut by 5.8 dB either way.

Double-click the plot to add one of four focus points. Drag a point up to cut more in that region, down to protect it. Wheel changes its width. Range handles on the plot drag the processing limits.

On the plot, the grey fill is the measured input. The bright line is what the detector hears (its smoothed spectral envelope); the dim line is what it expects there. Accent-coloured cuts appear where the bright line rises above the dim one by more than Threshold allows. The blue curve is the focus/protect shape.

Delta plays delayed dry minus wet before output trim. Use it to inspect changes, then return to normal monitoring to decide whether the music improved. Mix is a linear blend of aligned signals. Bypass keeps the same latency. Use Output for matched-level comparison. Spectral attenuation is not a limiter: sample peaks can increase even when frequency gains never exceed unity.

Four presets and A/B comparison help explore alternatives. Host parameters and window size persist; Delta does not.

How detection works

1. Each analysis frame is grouped into 512 log-spaced bands. Each band holds the mean power of the FFT bins it covers, smoothed over time (about 5 ms rise, 40 ms fall) so cuts hold on a stable ring instead of flickering.
2. Neighbouring peaks are joined in dB, so the gaps between harmonics do not count as the expected level. A plain harmonic tone reads as a smooth envelope.
3. The envelope is smoothed across frequency by the Sharpness width.
4. The reference is a robust local straight-line fit over 2–3 octaves: spectral tilt is expected, bumps cannot raise their own reference, and empty regions (below a fundamental, beyond a filter cutoff) are ignored.
5. Envelope minus reference is the band's height above its floor. Above Threshold it becomes a cut through the Knee and Ratio curve, limited by Depth, smoothed with Attack/Release, and linked across stereo.

Timing and limits

Mixing only: 2048-sample analysis windows at 44.1/48 kHz, 4096 at 88.2/96 kHz, 8192 at 176.4/192 kHz, with eight overlaps. Delay is one window, about 43–46 ms. The plugin reports it for host compensation. Supported layouts are mono and linked stereo; supported rates are those six standard rates.

The engine uses complex RustFFT with supplied scratch buffers, WOLA reconstruction, the envelope/reference detector above, bounded soft-knee cuts, and temporal smoothing. Original bin phases are retained. This is not a minimum-phase filter bank, a live monitoring effect, a limiter, or an automatic separation of tone and unwanted resonance. No external sidechain, Learn or M/S. The pitch detector serves Tone guard only.

Build and offline evaluation

cargo test --workspace --locked
cargo run --release -p patina-render -- input.wav processed.wav
cargo run --release -p patina-render -- input.wav delta.wav --delta
cargo run --release -p patina-render -- --demo /tmp/patina-demo.wav
cargo run --release -p patina-render -- --benchmark
python scripts/build-plugin.py --plugin patina --target x86_64-pc-windows-gnu

The renderer accepts mono/stereo PCM16/24/32 and float32 RIFF/WAVE, capped at 256 MiB; WAV extensible/RF64 are not accepted. It writes float32 WAV, compensates the processing delay, retains original duration, and refuses existing output. An optional settings JSON uses the core's Settings structure.

CI and acceptance

Gitea Actions cross-builds Windows binaries with MinGW on a Docker-capable runner labelled ubuntu-latest. Branch/PR workflows build a combined preview bundle; patina-v<version> tags check, build, and publish Patina independently. See release workflow for runner setup and release attachments. Actual runner execution remains to be verified on the Gitea instance.

Before calling host support complete, test FL Studio discovery as an effect, automation, plugin delay compensation, parallel dry/wet alignment, repeated loading, project restoration, mono/stereo, all supported sample rates, and render tails. Judge through real patches with matched listening levels: preserve vowel motion, snare punch, bass body, and stereo placement. Synthetic tests do not establish artistic usefulness.

Local benchmark, optimized build, stereo 48 kHz, FFT 2048/hop 256: five seconds processed in about 0.35–0.45 seconds (7–9% of one core on a laptop CPU). This is not a worst-case multi-instance guarantee.

Existing projects and source layout

The CLAP ID is now io.narl.bass-foundry.patina (earlier builds used io.storyboard.resonance-compressor). Hosts treat Patina as a new plugin, so add it again in projects saved with an earlier build. Version 0.2 replaced Amount, Sensitivity, Max cut, Neighborhood, Cut width, and Knee with Depth, Sharpness, and Selectivity; version 0.5 replaced Selectivity with Threshold (dB), Ratio and Knee, so projects saved earlier load Threshold at its default. Delete the old plugin file, place Patina.clap, and rescan FL Studio.

Source is grouped into plugins/patina/{core,ui,render,plugin}. See research, development, and the independent release workflow.