Reverb Module — Convolution Reverb

Convolution reverb using ConvolverNode with a decaying filtered noise impulse response, rendered asynchronously via OfflineAudioContext. Stereo spread via 3ms inter-aural delay on the right channel.

Available as a send effect in the sequencer (Reverb card in the master collapsible section, Snd tab per-sound send fader).

Signal Flow

input → preDelay → convolver → makeupGain (×2.5) → wetGain → outputL
                                                 → wetGain → outputR

The input is mono-summed (pre-delay is mono). The convolver output feeds a makeup gain stage (+8dB) to compensate for convolution energy loss, then splits to stereo outputs.

Impulse Response Generation

The reverb tail is rendered asynchronously via renderTail():

OfflineAudioContext(2, sampleRate × decay, sampleRate)
  → white noise buffer (full length)
  → highpass filter (lowCut, default 50 Hz)
  → lowpass filter (highCut, default 8 kHz)
  → exponential gain ramp (1 → 0.001 over decay seconds)
  → split L/R: L direct, R with 3ms delay
  → destination

The impulse response is generated on first build() and can be re-rendered at any time via renderTailAsync() (e.g. when decay or filter params change).

Parameters

Param	Range	Default	Description
`reverbMix`	0–1	0.4	Wet/dry blend
`reverbDecay`	0.3–10 s	2.5 s	Reverb tail length
`reverbPreDelay`	0–0.2 s	0.02 s	Pre-delay before reverb onset
`reverbLowCut`	20–500 Hz	50 Hz	Highpass filter on tail
`reverbHighCut`	500–20000 Hz	8000 Hz	Lowpass filter on tail

Exports

Export	Signature	Purpose
`paramDefs`	—	UI param definitions (5 params)
`build`	`(ctx, params)`	Create stereo reverb chain, returns `{ input, outputL, outputR, nodes }`
`update`	`(nodes, params)`	Update pre-delay and mix from params
`renderTailAsync`	`(nodes, params)`	Re-render impulse response with current decay/filter settings

Integration

As sequencer send FX

The reverb is wired in ensureMasterBus alongside stereo distortion:

engine._reverbInput = ac.createGain()
engine._reverbNode = reverbMod.build(ac, engine)
engine._reverbInput → engine._reverbNode.input
engine._reverbNode.outputL → _limSumL
engine._reverbNode.outputR → _limSumR

Per-sound send level is controlled via sound.sends.reverb (set in Snd tab). The reverb return injects post-glue-compressor, pre-brickwall-limiter so tails don't pump the compressor.

In a synth engine

Can be added to any engine's modules array for per-voice reverb.

Files

File	Purpose
`modules/reverb.js`	Module implementation (120 lines)
`sequencer-audio.js`	Master bus wiring (`ensureMasterBus`)
`sequencer-ui.js`	Master section Reverb card + Snd tab slider
`sequencer.js`	`_playNote` reverb send routing