88 lines
3.2 KiB
Markdown
88 lines
3.2 KiB
Markdown
# Wavetables
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Any sample can be played as a wavetable. When you use the `scan` parameter, the sample automatically becomes a pitched oscillator that can morph between cycles.
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## What is a Wavetable?
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A wavetable is a series of single-cycle waveforms stored end-to-end in an audio file. Each cycle is a complete waveform that starts and ends at zero crossing, allowing it to loop seamlessly at any pitch.
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```
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Sample: [cycle 0][cycle 1][cycle 2][cycle 3]
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↑ ↑
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scan 0 scan 1
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```
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The oscillator reads through one cycle at audio rate (determining pitch), while `scan` selects which cycle to play. Values between cycles crossfade smoothly, creating timbral morphing.
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## Basic Usage
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Just add `scan` to any sample and it becomes a wavetable:
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```forth
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pad 0 scan . ( play pad as wavetable, first cycle )
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pad 0.5 scan . ( blend to middle cycles )
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pad 440 freq 0 scan . ( play at A4 )
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```
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Without `scan`, the sample plays normally. With `scan`, it becomes a looping wavetable oscillator.
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## Parameters
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| Parameter | Range | Description |
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|-----------|-------|-------------|
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| `scan` | 0-1 | Position in wavetable (0 = first cycle, 1 = last) |
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| `wtlen` | samples | Cycle length in samples (0 = entire sample) |
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| `scanlfo` | Hz | LFO rate for scan modulation |
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| `scandepth` | 0-1 | LFO modulation depth |
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| `scanshape` | shape | LFO waveform |
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## Cycle Length
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The `wtlen` parameter tells the engine how many samples make up one cycle. This must match how the wavetable was created, otherwise you'll hear the wrong pitch or glitchy artifacts.
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```forth
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pad 0 scan 2048 wtlen . ( Serum-style 2048-sample cycles )
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pad 0 scan 1024 wtlen . ( 1024-sample cycles )
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```
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Common cycle lengths are powers of two: 256, 512, 1024, 2048. Serum uses 2048 samples per cycle. The number of cycles in a wavetable is the total sample length divided by `wtlen`. If `wtlen` is 0 (default), the entire sample is treated as one cycle. The sample still loops as a pitched oscillator, but `scan` has no morphing effect since there's only one cycle.
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## Scanning
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The `scan` parameter selects which cycle to play:
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```forth
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pad 0 scan . ( first cycle only )
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pad 0.5 scan . ( blend between middle cycles )
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pad 1 scan . ( last cycle only )
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```
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## LFO Modulation
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Automate the scan position with a built-in LFO:
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```forth
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pad 0 scan 2 scanlfo 0.3 scandepth . ( 2 Hz modulation, 30% depth )
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```
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Available LFO shapes:
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| Shape | Description |
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|-------|-------------|
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| `sine` | Smooth oscillation (default) |
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| `tri` | Triangle wave |
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| `saw` | Sawtooth, ramps up |
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| `square` | Alternates between extremes |
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| `sh` | Sample and hold, random steps |
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## Creating Wavetables
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A proper wavetable file:
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- Contains multiple single-cycle waveforms of identical length
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- Each cycle starts and ends at zero crossing for seamless looping
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- Uses power-of-two cycle lengths (256, 512, 1024, 2048)
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- Has cycles that morph smoothly from one to the next
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You can find wavetable packs online or create your own in tools like Serum, WaveEdit, or Audacity (using zero-crossing snap). Single-cycle waveforms also work. With `wtlen` set to 0, a single-cycle sample becomes a basic pitched oscillator.
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