Proper mastering is an absolute requirement for any recording before it can be played on any radio station. While mixing creates a CD that sounds correct in the studio, mastering modifies that CD so that it will sound correct outside of the studio, on the radio, on a home audio system, in the car, etc. Also during this process the individual songs are made to play at equal volume and with a common frequncy response curve so that the songs sound as if they are part of a comprehensive CD rather than separate songs. In addition to these important issues, it has become extremely important to radio stations and to record companies that CDs are recorded at as high a level (volume) as is possible without distortion. In some cases distortion is even becoming acceptable in order to squeeze out an extra couple of 'db' from the track. This is accomplished during mastering with the use of a device called a limiter. Mastering is the final opportunity to correct any problems with the CD.
