What is Mastering? It's the difference between a CD that sounds alright and a CD that sounds great. Mastering (for post production) is the important process that is done after mixing and before replication. It's the final phase of audio production that increases the volume of a recording and highlights details that aren't readily apparent. It can also reduce overall noise and help remedy “pops” or out-or-phase tracks. Radio stations compress the 'heck' out of songs; unmastered tracks will sound either muddy and bottom-heavy or tinny and weak. A CD may be played on anything from a rinky-dink boom-box to a top-of-the-line home system. A Mastered CD will sound great on any and everything.
Mastering Engineers hear differently than Tracking and Mixing Engineers. Mastering requires patient, careful listening. A Mastering Engineer may listen to several minutes of a song, over and over again, before making a single adjustment on an EQ or a compressor. Sometimes the Engineer will listen to an entire song, over and over again, just forming an opinion about what the mix needs, before doing anything at all to it. Unlike the relatively fast pace of mixing, Mastering is as much about considering options as it is about making changes.
Despite the strong creative element, Mastering is also about having high-level technical skills. A Mastering Engineer knows intimately how EQ and compression can affect the 2-track mix, and therefore how to apply it effectively to re-balance a mix. Mastering Engineers must have a thorough knowledge of digital audio, and how to squeeze the best possible sound quality out of digital audio productions.
Among the list of “most-used” tools of the Mastering Engineer are the compressor and limiter. The compressor and the limiter are considered “swappable” by many people because they can be used to address the same problems (situations). In fact, one unit can function either way: during recording. Mastering requires two separate units. Compress to shape the dynamics by adding snap, punch and strength. The limiter, by controlling the peaks, allows the Mastering Engineer to raise the level on the song.
The job is about creating a delivery Master from which hundreds, thousands, or even more CD's are made. The Mastering Engineer has a thorough understanding of digital audio, and how to correctly prepare a delivery Master for manufacturing CD's without defects.
If you read the credits on your CD's, you'll see that Mastering Engineers are rarely anything else. They are seldom, if ever, listed as any other kind of engineer. Mix Engineers often do recording sessions, and Recording Engineers often mix the projects they record, but Mastering Engineers only do one thing: MASTERING!