harshness detect:
http://www.noisebud.se/?page_id=765

To crunch harsh hi’s use a good bitcrusher. D16 Decimort is great.

https://www.soundonsound.com/sos/sep11/articles/mix-mistakes.htm
mixing plugins:
tools like the Melda MAutoEqualiser and Voxengo Curve EQ plug‑ins, or the off‑line Har-Bal software. Whatever any software tells you, though, be very wary if it contradicts the evidence of your own ears.

There are a number of dedicated phase‑adjustment plug‑ins worth investigating, including commercial products such as Audiocation’s Phase, Voxengo’s PHA‑979 or Littlelabs’ IBP Workstation (for the UAD2 platform), as well as freeware such as Betabugs’ Phasebug and Variety Of Sound’s new preFIX.

Be careful when layering several bass parts or low drum sounds within a single arrangement. Allowing such layers to slip in and out of phase with each other is a recipe for frustration, because it’ll cause the combined tone to change sporadically throughout the timeline in a way that’s almost impossible to fix with normal mix processing

Be wary of delay or reverb effects that take ages to decay at the low end, because they can quickly make an unpalatably thick soup of your sonics. In typical pop, rock and electronica work, you can usually afford to high‑pass filter most effect returns well above 100Hz, as well as applying additional LF shelving or peaking cuts in the couple of octaves above that.

Avoid EQ’ing in solo, because most people instinctively try to give every track a ‘forward’ sound if they work like that. It’s what your tracks sound like in the context of the mix that really counts.

It’s standard practice on a professional level to carefully automate lead vocals in order to maximise the intelligibility of the lyrics, so don’t forget to give that process the time it needs. While you’re at it, try fading up the ends of some of the note tails — you’d be surprised how often they contain characterful little bits of hidden phrasing that can really make a performance seem more emotional.