OTT Module — Multiband Upward/Downward Compressor

Multi-band compressor inspired by Xfer Records OTT. Splits the signal into low (≤250 Hz), mid (250–4 kHz), and high (≥4 kHz) bands using Biquad filters, then applies independent upward + downward compression to each band.

Signal Flow

input → split into 3 bands (LPF 250Hz / BP 1kHz peaking / HPF 4kHz)
  ├→ low band:  downComp + upComp × upGain + dry → sum × 1/3
  ├→ mid band:  downComp + upComp × upGain + dry → sum × 1/3
  └→ high band: downComp + upComp × upGain + dry → sum × 1/3
  → wetSum × depth → output
  └──────────────────────────────────→ dry × (1 − depth) → output

Each band's down compressor uses threshold and ratio from the Down param, while the up compressor has a fixed −60 dB threshold / 10:1 ratio with variable makeup gain from the Up param.

Parameters

Param	Range	Default	Description
`ottDepth`	0–1	0	Wet/dry blend
`ottDown`	0–1	0.7	Downward compression amount (threshold −20 to −50 dB, ratio 1–10:1)
`ottUp`	0–1	0.8	Upward compression makeup gain (0–+6 dB)
`ottAttack`	1–50 ms	3 ms	Compressor attack time
`ottRelease`	10–500 ms	80 ms	Compressor release time

Exports

Export	Signature	Purpose
`paramDefs`	—	UI param definitions (5 params)
`build`	`(ctx, params)`	Create OTT chain, returns `{ input, output, nodes }`
`update`	`(nodes, params)`	Update all band compressor params

Integration

Wired into engine chains via the backward loop as a processor module type. All six engines include OTT as the last processor before the master limiter.

Files

File	Purpose
`modules/ott.js`	Module implementation (136 lines)
All engine `modules` arrays	Included in every engine's processor chain