Well regardless of the problems that caused the issue he is currently having,. the fact is, the track has been recorded.
Possible ways you could deal with it:
- Sweep with a medium Q (not a crazy boosted high Q, you will fry your ears so quick) in the range you think the harshness is coming from until you zone in on it. Now bring that frequency down and find a good compromise between "less harsh but not killing the rest of the track"
- In addition to or alternative to the first idea, once you have identified the offending frequency zone, put on a de-esser tuned to that frequency and let it attenuate just those frequencies when they jump out. Your gain reduction you dial in will depend on just how badly you want to attenuate that frequency.
- In addition to the 2 above methods (or alternative) try some mild tape saturation to warm it up, round it off and beef it up a bit. There are lots of tape saturation
plugins but they all do different things. Some add audible distortion as effect while others do a good job at rounding out the sound and phattening it up without any crunch or audible distortion - in specific I am referring to the DUY DaD Tape plugin. That's my go-to tape plug for these scenarios. It Helps BIG time.
Good luck!