When plugged into a track, the AIR equalizer appears as a dark gray box and has three main knobs for adjusting high, middle and low frequencies. It is a limited machine because this equalizer's main ability boosts or diminishes the general area of the three frequencies and does not do much else. The band equalizers appear as white boxes with several more knobs and components than the AIR equalizer. With the band equalizers, you are able edit up to seven bands, or frequencies, and you can determine not only the exact frequency that will be affected, but how wide and narrow the range of each edited frequency will be.
When editing a rap vocal track, the high frequencies are often the most important frequencies. By boosting the highs one to three decibels, your vocal should stand out as words will all be clearer and more distinct. High-frequency boosting can keep a vocal track from blending with the rest of the background music. If equalizing the music or the entire song with the vocals included, an additional one- to two-decibel boost is appropriate. However, if you want the sound to be muffled, as if you were listening to the song from the outside of a building, you should dramatically lower or even completely eliminate the high frequencies.
The middle frequencies are most important on individual tracks that contain nonpercussive instruments. They can bring out or hide away the personality put into a guitar, piano or synthesizer recording. Mids are also commonly adjusted for small portions of an entire song, especially for intro sections. They will be lowered or removed altogether to create the sensation that the fullness of the song is not quite present. The purpose of this effect is to make the beat extra powerful when it "drops."
In rap and other hip-hop music, synthetic tonal bass and synthetic percussive bass are two of the most important elements in nearly every song. By boosting the lower frequencies on an entire project, you add a lot of power to these and other low-frequency sounds without affecting the rest of the song. Lower frequencies should never be removed, and the only reason that they should ever be lowered is if the individual instruments were all too loud to begin with.