From MusicBrainz Wiki
"Having both masters and tracks-with-MBIDs (as LordSputnik suggests)? I'm not sure what advantage that has over a three-tiered system."
- Masters mainly wouldn't be based on listening to the music. In my proposal, masters are created only where they're documented somewhere. This ties in with them being the place to put mastering relationships - generally the information on who mastered what will be enough to tell you if it should be a new master or not. Finally, masters would be optional - since a huge number of recordings/releases don't currently have associated production relationships, the corresponding track entities wouldn't end up related to masters. Also, masters would be related to mixes - so tracks would only share a master if they had the same mix. (So any remixes, mashups, etc. would use a different master, or, more probably, no master at all).