Let's Talk About 7 khz...

Let's talk about the frequency 7 Khz:
Need more "snare" sound from a dead snare - boost 7 Khz.
Need more "sizzle" in cymbals - boost 7 Khz.
Need less sibilance from vocals - cut 7 Khz (this can really be anywhere from 4 Khz to 9 Khz...but 7 Khz is the most common denominator for sibilance.
Need more "grit" in an electric guitar - you guessed it, boost 7 Khz.
Note: 7 Khz is the general area where these characteristics hang out. Your mileage may vary according to the instrument, but overall, the above will get you very close.