I'm working on a problematic mix for an aggressive rock band which I didn't record. Distortion everywhere, lack of clarity, resonant frequencies everywhere, etc.
In diving deep into every plugin I have looking for all solutions, I found that using the harmonics section in MeldaProductions MSaturator, and 'subtracting' 3rd harmonics is adding clarity, transients, life to the individual tracks and the mix.

But what is it actually doing? Is it actually reducing those harmonics in the signal or is boosting all of the others? Keeping overall 'gain' at 0, and just reducing '3rd'. Volume of track jumps and needs to be adjusted.

Picture of Harmonics section from MSaturator attached.

 

You can check this with a square wave generator and an fft analyzer.

 

Check what the plugin is doing with DDMF Plugin Doctor. (Hammerstein section)

 

I have checked it. It always adds moe harmonics, but in different ratios, depending on settings. So with this free plugin you always end up in oversaturation.