What is a Sidechain Input?

A sidechain input is an additional signal path used by certain audio processors, such as compressors or gates, to control how the effect behaves. Instead of responding only to the track it is processing, the plugin or hardware unit can react to a separate audio signal.

For example, in a common mixing technique called sidechain compression, a compressor placed on a bass track may use the kick drum as its sidechain input. Each time the kick drum plays, the compressor briefly lowers the volume of the bass, creating space for the kick in the mix.

Sidechain inputs are widely used in music production and sound design for creative and technical purposes. They can be used to create rhythmic pumping effects, improve clarity between instruments, trigger gates, or dynamically control processing based on another track in the session.