If your mix is lacking separation, width and depth, stem mastering can help you achieve this.
When we speak of stems we refer to work with subgroups extracted project mix. All the stems for a given master should be the same length, which when added back together at equal volume create the mix as if you had presented it as a single stereo file.
Stems should ideally number 6 or less. For example, a battery group, percussion, bass, vocals, melodic lines and fx´s.
It’s important to note that mastering from stems is not a substitute for doing a mix, the stems need to be created from a finished mix down.
It is not required always make 6 groups of items, if the mix is fine but there are doubts about the level of the vocal, only two groups would, one vocal and one with the other sounds. This process is not a mix itself, is not possible to fix a faulty mix, but allows us to solve some problems that we would not be solved with a single stereo file. With this option we can get a better tonal balance and a better balance of levels, when faced with the work of compression and limiting.