What's stem mastering and why should I use it?
Stem mastering designates the process of having multiple tracks (“stems”) at the mastering stage. Those tracks usually are a stereo sum of a group of musical sources. Here's a 3 stems example: Vocals, Drums and the rest of the instrumentation. If listened together, the sum of the stems should replicate the mix exactly.
Stem mastering is an ambiguous workflow that could harm the production cycle if not prepared correctly. Stem mastering incorporates some mixing decisions into the mastering process but shouldn't be used as a “second mix”. The consequences of doing so could be just that, having a second mix and not a proper mastering before release. Here's two good reasons to use a stem mastering :
- You're not sure about the vocal levels and wish to be able to change them slightly once the whole track is at the proper level.
- You wish to take advantage of having different treatments of two instrument sections even though you're happy with the mix.