Sidechain Ducking

Sidechain Ducking operator properties for Script Engine. Automatically lowers the volume of the layer's audio whenever a chosen "trigger" input is loud enough. The classic use is ducking background music under a voice-over, or dipping ambient room sound under a commentator — every time the speaker talks, the background gets quieter on its own, and recovers when the speaker pauses. Pick the trigger input via SidechainSource, then tune threshold, ratio, and attack/release for the feel.

Property	Type	Access	Description
`SidechainSource`	`StringCollectionEnum`	`get/set`	The input whose audio level drives ducking on this layer. Lists every audio-capable input in the project. Pick the voice/commentary mic when you want music to dip under speech. Set to `None` to disable ducking. The selection is remembered with the project.
`ThresholdDb`	`float`	`get/set`	Sidechain level at which ducking starts engaging, in dBFS. [min=-60, max=0, default=-30]. When the trigger input rises above this level, the layer starts to dip. Lower (more negative) values make ducking trigger more easily, even on quiet speech; higher values only react to clearly loud passages.
`Ratio`	`float`	`get/set`	How aggressively the layer audio is dipped once the threshold is crossed. [min=1, max=20, default=4]. 1:1 means no ducking. 4:1 (default) gives a typical music-under-speech feel. 10:1 or higher produces a very obvious dip. Higher values combined with a low `MaxGainReductionDb` give "radio-style" hard ducking.
`AttackMs`	`float`	`get/set`	How quickly the layer dips once the trigger crosses threshold, in milliseconds. [min=1, max=500, default=10]. Short attacks (1–10 ms) duck instantly — speech jumps to the front cleanly. Longer attacks (50–200 ms) produce a softer "fade-down" feel but let the start of the trigger spill through.
`ReleaseMs`	`float`	`get/set`	How quickly the layer comes back up after the trigger goes quiet, in milliseconds. [min=10, max=2000, default=200]. Short releases recover quickly between words but can sound "pumpy" on continuous music. Longer releases (500–1500 ms) keep the layer down across natural pauses and recover smoothly only when the speaker really stops.
`MaxGainReductionDb`	`float`	`get/set`	Hardest dip allowed on the layer audio, in decibels. [min=-48, max=0, default=-20]. −20 dB is a typical value — music is clearly under the voice but still audible. −6 to −12 dB gives a gentle dip; −30 dB or more makes the layer almost disappear. 0 dB disables ducking by allowing no reduction at all.
`GainReductionMeter`	`GainReductionMeterData`	`get`	Live readout of how much the layer audio is being dipped right now, in dB (read-only). 0 dB means ducking isn't currently active. Negative values show active ducking — the more negative, the harder the dip. Useful for tuning threshold and ratio against real material.
`SidechainLevelDisplay`	`AudioMeter`	`get`	Live level of the trigger input, in dBFS (read-only). Compare against `ThresholdDb` to see when ducking will engage. Shows "—" when no `SidechainSource` is selected or the signal is silent.
`ResetCommand`	`Command`	`get`	Reset all settings to their defaults (−30 dBFS threshold, 4:1 ratio, 10 ms attack, 200 ms release, −20 dB max reduction).

Inherits from: AbstractAudioOperator, AbstractOperator, AbstractAudioMetering.

See also: Sidechain Ducking in Operators — user-facing introduction, screenshots, and section summaries.