EQ is one of the fundamental tools in the mixer’s arsenal. When asked if he couldn’t live without compression or EQ, recording and mixing educator Joe Gilder replied “unequivocally it would be EQ.”
There are a number of reasons EQ is such a powerful tool. It can be used to substantially shape the tone of a musical source. It can be used to remove offensive tones from recordings. It can be used subtly to help varying tracks fit together in a complete mix without stepping on each other (technically frequency masking).
Often this fitting of the tracks is accomplished by removing frequencies from tracks that don’t need them (or need them less than other tracks) so that in those other tracks those frequencies can be heard. Thus clarifies the instrument without needing to boost those frequencies.
Many mixers take this cut first philosophy for a few reasons. One is that when cutting rather than boosting one is less likely to fall into the boost, boost, boost, boost, why can’t I hear anything? trap. Second, any EQ that is not specifically a linear phase EQ imparts a phase shift to the signal when the specific frequencies are separated to be boosted or cut. Whether this phase shift is good or bad (or whether you can even hear it) is up to the individual mixer. However, it is true that by cutting rather than boosting, the resulting phase shift is quieter rather than louder.
All that being said, boosting for the sake of tonal shaping should never be overlooked. I will cut first as a rule, but will boost when the situation calls for it.
After this long introduction, this installment of Best of the Web includes a five article series from The Cakewalk Blog detailing how to use subtractive EQ to help the elements of a rhythm section gel together in a mix.