Equalization, from a musical perspective, is the act of changing the frequencies and sounds of a song. You've likely heard most of these frequencies at one time or another. Sound frequencies can be described as terms such as bass and treble. There are many instruments that can be found in any musical composition. The music might sound fantastic to the casual listener, but it could sound off for professionals. Audio equalizers are used to remove or filter certain frequencies in order to create a perfect harmony.