This is an audio plugin written in FAUST that automates gain level adjustments, based on a target gain level, a time window over which overall loudness is calculated via RMS, and a maximum adjustment threshold.
This plugin is comparable to Waves Vocal Rider or Waves Bass Rider in its functionality, but is free and open-source.
Grab the latest release from https://github.com/unicornsasfuel/levelrider/releases that corresponds to your operating system and supported plugin type, unzip it if it is zipped, and drop the file into the appropriate plugin directory or run the installer package.
Help finding VST3 locations can be found here: https://helpcenter.steinberg.de/hc/en-us/articles/115000177084-VST-plug-in-locations-on-Windows
Help finding AU locations can be found here: https://support.apple.com/en-us/HT201532
Since making macOS plugins that do not trigger Gatekeeper requires paying Apple $99 USD/yr for a developer license and I am not profiting from this software, this plugin will trigger Gatekeeper. Right click the installation package after downloading, and click "Open". When the prompt appears, click "Open" again to install the plugin.