Equalization (or EQ) refers to the adjustment of audio frequencies produced by multiple instruments and tracks in a song, which can either be cut or boosted to reduce or increase the presence of specific frequencies or frequency bands. This is done to improve the audio aesthetics of an entire track.
EQ may also be used to eliminate or reduce unwanted sounds and transients, and altering EQ is a good way to adjust the timbre of a song or track by modifying the substance of its frequencies. This can furthermore assist in shaping and glueing tracks within the sonic spectrum and overall context of the mix.
Depending on the objective of the project, different EQ units will deliver different tones and character to a song.
Some popular choices include:
Equalizers for Song/Production/Mix Bus processing should be two-channel stereo units or a stereo pair of mono units.