Waves Primary Source Expander

PSE lets you reduce stage bleed and sensitivity to feedback when a mic is idle by automatically lowering mic levels between musical phrases. Perfect for live sound and for mixing live recordings.
At the heart of the Primary Source Expander (PSE) plugin is a precision expander, tailored especially for melodic sources such as vocals, guitars, strings, brass, woodwinds and more. PSE works like a fader that smoothly attenuates the channel’s level when the source goes below the threshold you’ve set. You determine both the threshold and the amount of attenuation.
Reducing stage noise leakage when your microphones are idle will help you get an overall mix that is more coherent, more focused, and has better phase relations.

PSE also provides advanced sidechain and ducking controls for greater consistency and precision when treating complex live scenarios. Whether you are mixing FOH or monitors in a live venue or working on a live recording in the studio, PSE will ensure that your mics are as loud and clean as they can be, while preserving your source’s original tone and the natural ambience of your location.