Mastering is an art form and finishing step, not an automatic device audio is run through
Mastering is the intermediate step between mixdown and replication or distribution — but it is not a set of tools or a ‘mastering device’ that music runs through and comes out mastered. Done at its highest form it is an art form that relies on an individual’s skill, experience across genres, and taste. The common misconception is that a plug-in labelled ‘mastering’ can substitute for this judgement.
Examples
A mastering engineer receives a mixdown, adjusts EQ and dynamics for cohesion, inserts spreads between songs, sequences the tracks, proofs for errors, and delivers a verified master — decisions no automatic ‘mastering device’ makes for you.
Assessment
What distinguishes mastering as an art form from simply running audio through a ‘mastering device’?