Check
www.artistpro.com
They have on-line classes there that teach you a lot on this kind of stuff. I remember under "Dynamics" topic I read about doing the same thing someone just said: Run the sound through an EQ, boost the frequencies causing the problem, then run the new sound through a compressor with the appropriate ratio so that those problem-frequencies get compressed.
However be very carefull with attack & release time setting:
"If the attack time is too fast, the compressor will turn down the transients. This can cause an instrument to lose life and clarity. On a vocal, for instance, if the attack time is too fast, all of the “t” and “s” sounds will start to disappear. On the other hand, if the attack time is too slow and the vocal is very compressed, the t’s and s’s will fly through uncompressed and sound exaggerated"
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