Well, Ozone comes with one of those (seems to behave kind of like a dynamic EQ with transient shaping) - but unless we’re talking really nasty problems, or sound design, the first step is usually the EQ.
Synths can easily be extremely harsh, and some instrument/mic combos aren’t particularly pleasant sounding out of the box either, but in many cases, it’s just that timbre, resonances, mic coloring etc adds up, and it’s often enough to just correct it with an EQ.
If that doesn’t cut it (pun intended); if the sound goes dull and muffled before you get that harshness out, the next thing to try would be a dynamic EQ, multiband compressor, or de-esser. They all do basically the same thing: Compress or expand specific frequency ranges. The difference is mostly what kind of problems they’re optimized for.
For example, if you have a synth that’s constantly harsh sounding, but attenuating the problematic frequencies just makes it sound muffled, you might try making that band dynamic instead, expanding the dynamic range a bit, so that the offending harshness is reduced a lot, but the EQ opens up and lets a bit of “bite” through in the attacks.
Of course, the best solution is usually to make sure the source sounds nice in the first place. “Real” synthesis is so much nicer than samples in that way; you can tweak literally everything, and that means more control and less artifacts. But, with the nice dynamic EQs, MB compressors, and indeed, spectral shapers and whatnot we have these days, sometimes it’s quicker and easier to just shape things up there instead, or at least do the final tweaks there, after fixing the big issues at the source.
Now, speaking of spectral shaping and harshness, here’s a use case for kiloHearts Multipass:
- Set up one band to cover the problematic frequency range.
- On that band, add:
- Transient Shaper
- Frequency Shifter or Pitch Shifter (which one works best depends on the input)
With this, you can change the level and dynamics of the problem area, and also shift it to a different frequency range, and make it “punchier” or “snappier.”