Mixing is balancing multi-track audio files using faders, (i.e. kick, snare, toms, cymbals, bass, keys, lead vox, brass, strings, backing vox) in mixing there is discrete control over all the elements of a multi-track recording which is usually automated to a high degree.It is a time consuming procedure.

Each sound source runs through a mixer channel where discrete processing and automated levelling can be applied.It is different to stem mastering. And includes mastering process in it.