> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nomn.jp/llms.txt
> Use this file to discover all available pages before exploring further.

# Pitch Gravity Logic

> Scale quantization and ADP psychoacoustic enhancement

Controls how bubble pitches relate to musical scales, and adds psychoacoustic processing for melodic clarity.

## Scale Selection

| Control   | What It Does                                                                                                                                                            |
| --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Scale** | Choose from 75+ scales including Western modes, world scales, microtonal systems, and experimental tunings. The dropdown shows intervals (e.g., "Major: 2-4-5-7-9-11"). |
| **Root**  | The root note of the selected scale (C through B).                                                                                                                      |

## Quantization

| Knob         | What It Does                                                                                                                                                      |
| ------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Quantize** | How strongly bubble pitches snap to scale notes. At 0%, pitches are free and continuous (raw physics). At 100%, all pitches quantize to the nearest scale degree. |

When a scale is selected, **incoming MIDI notes** are also snapped to the scale before being used to compute bubble pitch — so an arpeggiator or sequencer outputting non-scale notes still produces in-key bubbles.

## Snap (Auditory Distortion Products)

| Knob     | What It Does                                                                                                                                                                                        |
| -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Snap** | Drives the **ADP engine**, which spawns psychoacoustic distortion-product partners alongside each main bubble. Low values add subtle spectral richness; high values create dense inharmonic clouds. |

The Snap knob is FOAM's most distinctive sound-shaping control after Rate and Size. It synthesizes auditory distortion products — the same combination tones your ear generates when two close frequencies sound together — and emits them as physical bubbles. The result is content the ear hears as "rougher" or "more present" without literally adding harmonics.

<Tip>
  Snap is independent of pitch quantization — you can have free continuous pitches with heavy ADP processing, or perfectly scale-locked melodic mode with no ADP at all.
</Tip>