Release groups usage guideline
Current Musicbrainz server release feature a concept called Release Groups. Just as the name suggests, it groups several releases together in one entity. Since this is not obviously clear, this page explains the difference and gives some guidelines on how to handle them.
Both release groups and releases are "albums" in colloquial sense, but with a slight difference: a release is something you can buy as media, e.g. a CD box, a vinyl record etc. on its own, while a release group embraces the concept of an album -- it doesn't matter how many CDs or editions/versions it had. When an artist tells you "We've released our new album", he's talking about a release group. When his publisher says "This new album gets released next week in Japan and next month in Europe", he's talking about several releases belonging to the release group the artist has told you about.
Therefore a single release group could contain:
- Plain releases consisting of one or more discs, e.g. Nirvana's album "Nevermind" or Linkin Park's single "Bleed It Out".
- Multiple-disc releases, including various artist compilations, like "Bravo Hits 64" and Richard Wagner's 10-disc release "Ring der Nibelungen".
- Different (special) editions with additional or alternative tracks or discs, e.g. Slipknot's "Vol. 3: (The Subliminal Verses)"
- Re-releases and re-masters, e.g. Blind Guardian's "Nightfall in Middle-Earth" released in 1998 and then in 2007.
A release group should not consist of:
- Complete compilation series' that have different volumes released over time. Typical examples are "Café del Mar", "Hitzone", "Ministry of Sound" and "Now That's What I Call Music!". Each volume of the series consisting of multiple discs can be a release group though.
- Different bootleg recordings of a live show, e.g. bootleg 1 and bootleg 2 of a 1970 Pink Floyd concert in San Francisco.
Musicbrainz automatically considers every release in the database to be part of a release group, even if this group only contains this one release. You don't have to worry about creating release groups, you only ever need to merge them.