History:What Defines A Unique Release

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When does a work actually become a "separate record" from MusicBrainz point of view? This is a somewhat complex issue which relates to both the current data model we are using, the tagging service, and to some extent the way users interact with the data. MusicBrainz has been widely hailed for its GUID approach to identifying music, but what does this exactly mean?

Roughly, that MusicBrainz base data units are unique sets of recordings.

Hence, a release which is a reissue (or reprint) of another (same recordings, same TrackTitles, same track times, same ReleaseTitle, same ReleaseArtist) is not considered to be a different release and should not be duplicated. Rather, you may enter an additional ReleaseEvent for it.

Now, in the real world, there is nothing like an exactly identical reissue (even the same edition may present some variants between units, depending on the plant that manufactured it for example), and the differences between reissues may be huge.

Though, we usually don't create a different release entry in the database for any of the following reasons (assuming the two releases contain the same tracks presented in the same order):

All these cases are detailed below with some additional information that you may find helpful to sort out non-straightforward cases.

Case by case detail

What if the cover picture/photo, or more generally the packaging is different?

Don't duplicate.

What about different formats? (Cassette vs Vinyl vs CD)?

They should not be duplicated. As a side-note, multi cassette and multi-vinyl sets should be treated the same way as multi-cd sets - each disc of the set should be filed separately in the database, following DiscNumberStyle.

But the track times are (slightly) different...

It's almost impossible to obtain a "standard" track time from a vinyl, or a cassette. Furthermore, pressings from different plants (for the very same edition) may very well have slightly different tracktimes (even for cd). Also, please remember that track times in MusicBrainz come from a number of different sources, and they may not be trusted up to 10 seconds differences (eg: homebrew cd copies may very well add/remove multiple 2 seconds gaps).

Hence, track times differences up to 10 seconds is usually not a reason to duplicate. On the other hand, though, if the difference is more than that, or if it's known that the two songs are indeed different recordings (eg: remix, single version, etc), then there should be two different releases.

What if the TrackTitles present minor variations (eg: spelling, punctuation, additional extra title information like "take")?

Don't duplicate.

What if one track has multiple (completely) different known titles in different reissues?

This cover several cases:

Usually, this is not a reason to duplicate the release.

You may use the correct title for the track (see ArtistIntent and possibly ConsistentOriginalData for some information about how to determine that), and either mention the alternative title in the TrackTitle itself (eg: "Official Title (a.k.a. Alternative Title)"), or use the ReleaseAnnotation for that.

What if the ReleaseArtist is different?

This boils down to how different.

What if the ReleaseTitle is different?

Here again, it's a matter of how much different: addition/omission of definite articles, slight spelling alterations, addition/omission of a subtitle are usually not considered a reason to duplicate.

What about promotional copies?

You shouldn't create duplicate entries for promotional copies that are identical in content to the official release.

What about remasters?

This is a touchy topic, for the reason "remastered" is not a clearly defined concept, and labels tend to print "remastered" on releases for very various and puny reasons.

Usually, you should not create duplicates for remasters, unless there are significant changes in the audio. For example, most jazz (and possibly classical) reissues advertised as "remastered" are not worth the duplication (most are nothing more than analog to digital transfers).

What if one of the edition has different/additional AdvancedRelationships that don't apply to the other editions?

That generally include cover art or liner notes credits, or possibly production credits (for the re-release).

This again is not a reason to duplicate. You may use the ReleaseAnnotation to mention to which edition such a specific credit applies.

What about BoxSets?

A BoxSet consisting exactly of a set of discs previously released in a standalone form should not be added (see BoxSetNameStyle), but the standalone discs instead. That obviously means that such a BoxSet discs may be merged into the standalone versions.

Now, please pay special attention to the facts that:

What about 2 discs editions that contain a BonusDisc?

Titling of such editions is addressed by BonusDisc and BonusDiscStyle. The "main" disc of such editions should not duplicate the standalone edition (assuming of course their content is identical).

Other non-duplication cases

There are even cases where there really is a substantial difference between two releases (eg: really different track length), but still the artists subscribers decided not to duplicate for a number of reasons. Ultimately, as stressed earlier, it's in the end a matter of common sense.

But are we going to lose all these fine grain differences between editions?

No, it's not lost. You should use ReleaseAnnotations to store any relevant details (alternate spellings, edition specific information, etc).

When NOT to merge, and keep "duplicates"

On the other hand, in the following cases, different releases should be kept separate.

Obviously, there should be multiple different entries in the database if:

But why not duplicate everything after all?

Our approach is different than Discogs': we don't keep one separate entry for each and every reprint, but rather one different entry per different track-set (eg: different recordings, or same recordings presented in a different order).

That approach being at the heart of both our current data model and tagging service, trying to duplicate anyhow will have several bad impacts:

Relevant readings

This page is transcluded from History:What Defines A Unique Release.