Stem Mastering
Definition
A mastering approach in which the client delivers grouped submixes (stems) — typically drums, bass, music, and vocals — rather than a single stereo mix. This gives the mastering engineer the ability to make targeted adjustments to individual groups, offering more flexibility than traditional stereo mastering while remaining less invasive than a full mix revision.
In Simple Terms
Instead of sending one stereo file to your mastering engineer, you send separate groups — drums, bass, vocals, everything else. This gives them more control to fix issues without affecting the whole mix. It costs more and takes longer, but the results can be significantly better if your mix has specific problems.
In Practice
A stem mastering session receives four stems: drums, bass, instruments, and vocals. The mastering engineer applies de-essing to the vocal stem and tames a resonant bass note without affecting the drum transients — adjustments impossible in a single stereo master.
Common Confusion
Stem mastering is not the same as mixing. The mastering engineer works with pre-mixed groups, not individual tracks. If a vocal needs its delay changed or a guitar needs re-panning, that requires a mix revision, not stem mastering.