Mastering is the term most commonly used to refer to the process of taking an audio mix and preparing it for distribution. There are several considerations in this process: unifying the sound of a record, maintaining consistency across an album, and preparing for distribution.
The most essential in audio mastering
The goal of this step is to correct mix balance issues and enhance particular sonic characteristics, taking a good mix (usually in the form of a stereo file) and putting the final touches on it. This can involve adjusting levels and general “sweetening” of the mix. Think of it as the difference between a good-sounding mix and a professional-sounding, finished master.
This process can involve adding broad equalization, applying compression, limiting, etc. This is often actually referred to as “premastering” in the world of LP and CD replication, but let’s refer to it as mastering for simplicity.
Mastering Before and After
Here are two examples from different genres, both pre and post mastering, to illustrate the sonic differences that can result from the aesthetic choices made by different mastering engineers.