Feat: refactoring codebase

2026-02-16 16:00:57 +01:00
parent c749ed6f85
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+# Filters
+
+Filters attenuate frequencies above or below a cutoff point.
+
+## Lowpass Filter
+
+The lowpass filter (`lpf`) attenuates frequencies above the cutoff.
+
+```forth
+saw 1000 lpf .               ( cut above 1000 Hz )
+saw 500 lpf 0.8 lpq .        ( with resonance )
+```
+
+| Parameter | Range | Description |
+|-----------|-------|-------------|
+| `lpf` | Hz | Cutoff frequency |
+| `lpq` | 0-1 | Resonance (peak at cutoff) |
+
+## Highpass Filter
+
+The highpass filter (`hpf`) attenuates frequencies below the cutoff.
+
+```forth
+kick 200 hpf .               ( cut below 200 Hz )
+pad 400 hpf 0.3 hpq .        ( with resonance )
+```
+
+| Parameter | Range | Description |
+|-----------|-------|-------------|
+| `hpf` | Hz | Cutoff frequency |
+| `hpq` | 0-1 | Resonance |
+
+## Bandpass Filter
+
+The bandpass filter (`bpf`) attenuates frequencies outside a band around the center frequency.
+
+```forth
+noise 1000 bpf 0.7 bpq .     ( narrow band around 1000 Hz )
+```
+
+| Parameter | Range | Description |
+|-----------|-------|-------------|
+| `bpf` | Hz | Center frequency |
+| `bpq` | 0-1 | Resonance (narrower band) |
+
+## Filter Slope
+
+The `ftype` parameter sets the filter slope (rolloff steepness).
+
+| Value | Slope |
+|-------|-------|
+| `1` | 12 dB/octave |
+| `2` | 24 dB/octave (default) |
+| `3` | 48 dB/octave |
+
+```forth
+saw 800 lpf 3 ftype .        ( 48 dB/oct lowpass )
+```
+
+## Filter Envelope
+
+Filters can be modulated by an ADSR envelope. The envelope multiplies the base cutoff:
+
+```
+final_cutoff = lpf + (lpe × envelope × lpf)
+```
+
+When the envelope is at 1.0 and `lpe` is 1.0, the cutoff doubles. When the envelope is at 0, the cutoff equals `lpf`.
+
+```forth
+saw 200 lpf 2 lpe 0.01 lpa 0.3 lpd .   ( cutoff sweeps from 600 Hz down to 200 Hz )
+```
+
+| Parameter | Description |
+|-----------|-------------|
+| `lpe` | Envelope depth (multiplier, 1.0 = double cutoff at peak) |
+| `lpa` | Attack time in seconds |
+| `lpd` | Decay time in seconds |
+| `lps` | Sustain level (0-1) |
+| `lpr` | Release time in seconds |
+
+The same pattern works for highpass (`hpe`, `hpa`, etc.) and bandpass (`bpe`, `bpa`, etc.).
+
+## Ladder Filters
+
+Ladder filters use a different algorithm (Moog-style) with self-oscillation at high resonance.
+
+```forth
+saw 800 llpf 0.7 llpq .      ( ladder lowpass )
+saw 300 lhpf 0.5 lhpq .      ( ladder highpass )
+saw 1000 lbpf 0.8 lbpq .     ( ladder bandpass )
+```
+
+| Parameter | Range | Description |
+|-----------|-------|-------------|
+| `llpf` | Hz | Ladder lowpass cutoff |
+| `llpq` | 0-1 | Ladder lowpass resonance |
+| `lhpf` | Hz | Ladder highpass cutoff |
+| `lhpq` | 0-1 | Ladder highpass resonance |
+| `lbpf` | Hz | Ladder bandpass cutoff |
+| `lbpq` | 0-1 | Ladder bandpass resonance |
+
+Ladder filters share the lowpass envelope parameters (`lpe`, `lpa`, etc.).
+
+## EQ
+
+The 3-band EQ applies shelf and peak filters at fixed frequencies.
+
+```forth
+kick 3 eqlo -2 eqhi .        ( +3 dB at 200 Hz, -2 dB at 5000 Hz )
+snare 2 eqmid .              ( +2 dB at 1000 Hz )
+```
+
+| Parameter | Frequency | Type |
+|-----------|-----------|------|
+| `eqlo` | 200 Hz | Low shelf (dB) |
+| `eqmid` | 1000 Hz | Peak (dB) |
+| `eqhi` | 5000 Hz | High shelf (dB) |
+
+## Tilt EQ
+
+Tilt EQ applies a high shelf at 800 Hz with up to ±6 dB gain.
+
+```forth
+pad -0.5 tilt .              ( -3 dB above 800 Hz )
+hat 0.5 tilt .               ( +3 dB above 800 Hz )
+```
+
+| Parameter | Range | Description |
+|-----------|-------|-------------|
+| `tilt` | -1 to 1 | High shelf gain (-1 = -6 dB, 0 = flat, 1 = +6 dB) |