Amplitude Imposer is a free compressor VST plugin developed by ndc Plugs. Compatible OS(s): Windows, macOS.
Amplitude Imposer takes two stereo inputs, and imposes the amplitude envelope of the first one onto the second. It also has a feature where you can set a threshold level, and whenever the second signal’s amplitude falls below it, it is automatically amplified up to the threshold, in order to give a more constant signal to the amplitude imposer part.
It’s kind of like a compressor, but backwards.
http://www.niallmoody.com/ndcplugs