This article covers equalizers, and how to effectively use them in the mixing process. The equalizers role in a studio is to adjust frequencies of a source to better fit an application. You can boost a certain frequency band, attenuate a problematic area in a source, or adjust a sound to fit better in a mix.
Equalizers come in mono or stereo, the latter having the ability to make identical adjustments to both the left and right channels of the stereo track simultaneously. This is useful for tweaking a stereo tracked instrument or an overall mix, avoiding odd phasing issues that you may encounter if there were separate mono controls for both channels. Every EQ has separate control parameters specific to that EQ, but all EQs share a few main parameters.
Some EQs have a visual graph to show you how you are affecting the sound. The audible frequency band is on the X axis (horizontal) and the boost/cut is on the Y axis (vertical). On Equalizers, we have points in the spectrum we can manipulate called bands. These bands are not fixed in one particular spot, and allow you to find and manipulate the frequencies you want to for that particular application. These bands also overlap, giving you full control over the frequency spectrum and individual boost/cut control for each band. The bands can also be widened or narrowed in order to allow you to work with either large sections of the spectrum or precise frequencies. This is useful when you have a very specific problem area that needs attention, but you would like to leave the neighboring frequencies untouched. You should take some time to run several different signals through an equalizer in order to familiarize yourself with frequency bands.
EQs can both boost and cut certain frequency bands to get you the desired sound you are looking for. While there are no rules on how you use equalizers, you may find that cutting frequencies can be more effective than boosting. For instance, if you would like a certain band to pop out a little more, try lowering those frequencies on a conflicting track that may not need them as much. This will carve out a space for the original track to shine through, as it is not fighting for real estate on that particular band of the spectrum. You will also find that lowering one frequency band will inevitably raise another. For example, if you want a track to sound brighter, instead of boosting the highs, try lowering the lows.