This is the heart of FOAM’s sound generation. These controls determine the fundamental character of your bubble sounds.
Primary Emission
| Knob | What It Does |
|---|
| Rate | How many bubbles are emitted per second. At minimum, you get sparse individual pops. At maximum, a dense foam cascade. Exponentially scaled — small movements at the low end create subtle changes, while the upper range gets dense quickly. |
| Size | The physical size of bubbles (0.1-50 mm radius), which directly determines pitch via the Minnaert resonance equation. Larger bubbles = lower pitch, smaller bubbles = higher pitch. |
| Ring | How long each bubble resonates after bursting (5-625 ms). Short times give crisp pops; longer times create sustained, bell-like tones. Default is 125 ms (physically realistic). |
Cascade & Movement
| Knob | What It Does |
|---|
| Cascade | When a bubble bursts, it can spawn child bubbles. At 0, bubbles are independent. Higher values create chain reactions — foam avalanches where one pop triggers many. |
| Glide | Portamento between bubble sizes. At 0, each bubble has its exact size. Higher values smooth the transition, as if bubbles are expanding or contracting as they rise through liquid. |
Realism Physics
| Knob | What It Does |
|---|
| Shimmer | Real bubbles aren’t perfect spheres — they wobble and deform. This adds subtle pitch modulation, creating organic “chorus-like” movement. |
| Natural Balance | Controls the natural amplitude relationship between bubble sizes. At 100% (physics-accurate, the default), large bubbles are louder than small ones. At 0%, all bubbles have equal loudness regardless of size. |
| Jets | When bubbles burst at the surface, they can produce secondary “plink” sounds. Adds the characteristic rain-drop-on-water quality. |
Flow Type
The Flow Type dropdown controls the statistical pattern and pitch behavior of bubble emission:
| Mode | Character |
|---|
| Poisson | Random, natural timing — like champagne fizz |
| Nucleation | Bubbles emerge in clusters from nucleation sites |
| Foam Raft | Dense, raft-like emission patterns |
| Turbulent | Chaotic, swirling emission timing |
| Melodic | Each MIDI note plays one tightly-pitched bubble — turns FOAM into a melodic instrument |
| Harmonic | Bubbles spread across the selected scale around the played note — chordal/harmonic textures |
Melodic and Harmonic modes also activate pitch-tracking on the Resonator (in Fluid Dynamics) — the resonant body retunes itself to whichever note you’re holding. Combine with the Cave or Cistern preset for tunable cinematic textures.
