Traditional
Traditional because a finished, mixed material must be "brought to life." In a good case, the mixing is not unnecessarily compressed, is proportionate in both tonics and levels, and is sufficiently dynamic. In this case, there is a way for the mastering engineer to work nicely. Mostly in a DAW, digitally. But it can also be mixed with analog inserts.
Full analog
In special cases, the material may be handled on completely analogous devices. It has its charm, but is also more complicated, slower, and more expensive. Something for something...
Group and track mastering
There are times when we handle only part of the mixing. An instrument, or vocal track, or a group of instruments, a choir. By putting them back into the mix, the sound engineer can get better, more beautiful results in the blended material.
Stem, or group mastering
Perhaps this process may be most effective when the finished mixed material is obtained by grouping (groups 4-6-8) and thus working with the otherwise finished mixing. Already automated, mixed groups have the most and most accurate options for mixed material manipulation. Reassembling the groups can result in a very effective end result.
Remastering
This is an interesting procedure when we want to renovate the sound of older recordings, to make them more enjoyable and beautiful. (Not restoring, that’s another story.) There’s a lot of adventure in it, but sometimes it gives amazing results. Of course, it doesn't matter if the MUSIC is worth it!