Mastering in Music: What It Means and What It Does
Mastering is the last step between a finished mix and a released track. The mastering engineer takes the stereo mix as one object and adjusts its tone, dynamics, loudness, and stereo balance so it holds up on every playback system, then produces the exact files each destination needs. On an album, it is also the work that makes a dozen separately mixed songs sound like one record.
What mastering means
The word comes from the master: the single authoritative copy that every other copy is made from. The streaming transcode, the vinyl lacquer, the CD glass master, the file your distributor ingests, all of them are generated from that one file. Mastering is the work of making that copy correct, because nothing downstream can improve on it.
In practice it is a small number of decisions applied across the entire track at once. That constraint is the whole character of the job: a mastering engineer usually moves things by 0.5 to 2 dB, not by 10, because anything larger drags every element in that frequency range along with it.
