Mastering
Technical final processing of a sound recording as the last step before release.
What it means
Mastering is the final technical processing of a sound recording and the last step of a music production before release. The starting point is the finished mix, usually as a stereo file. In mastering, tonal balance, loudness and dynamics are adjusted so that the piece sounds equally good on headphones, loudspeakers and a car radio.
This includes the use of equalisation and compression, the limiting of peak levels, the setting of gaps and the running order of an album's tracks, and the addition of identifiers and metadata for the given format.
Musical use
Today mastering describes the step that prepares recordings for CD, vinyl and streaming. Vinyl records require different adjustments from digital formats. Streaming services also adjust loudness themselves, so extreme loudness has lost its advantage.
Mastering should be distinguished from mixing: in mixing the individual tracks are balanced against one another, while in mastering the finished result is treated as a whole. Mastering cannot rescue a weak mix; it only gives the final polish.
Performance practice
Listen to your piece on several devices before mastering and note what is missing. Leave enough headroom in the mix so that the mastering step does not have to work against distortion.