Mastering in Stems
This refers to a mastering technique whereby the mix is broken down into 3 to 4 stereo submixes. Each stereo pair is complete in itself (with all effects, dynamics…), which I then put together in the mastering process.
These submixes are delivered instead of a single stereo mix.
The 3-4 submixes can contain:
Foundation:
Normally the drums and bass. It
can, however, include rhythm guitar or piano if they are a part
of the same rhythmic figure . In trios, the bass is often counted
as part of the rhythm section because it is usually producing a
separate rhythmic figure .
Chor / Pad:
This includes sustained sounds, usually from organs or synthesizers.
String instrumentals such as power chords from a guitar also belong
to this submix, as do the backing vocals.
Rhythm:
This submix contains any instrument playing
a rhythmic figure that differs from the foundation. This could
be a tambourine, shaker, rhythm guitar, piano etc… anything producing
a counter-rhythmic figure .
Solo/lead:
Usually the main vocals, but also solo instruments.
The benefits:
The mastering engineer is able to access individual submixes,
which gives him much more flexibility in adjusting the relative
volume levels and sound. His job becomes an extension of that of
the mixing engineer, with the advantage of it being easier in a
controlled acoustic environment (mastering studio) to find the
optimum balance for your music.