When to merge recordings?

I’m not aware of any guidelines for merging recordings accept for: https://musicbrainz.org/doc/Edit_Types/74 and there are often heated discussions in the edit notes about what is enough evidence to merge recordings. E.g. tonight I got about 60 emails from edit discussions between @jesus2099 and @dragonzeron. I think it would be better to discuss this in the forum.
So I’d like to share my personal guidelines and see what you think about them.

I have three rules for merging recordings (either so I will merge or I will vote yes):

  1. There can’t be any obvious contraindications (e.g. different artist, recording title, length, recording disambiguations or even album disambiguations [e.g. one is clean the other explicit] or e.g. one is on a DJ mix).
    • if you can plausibly explain why it’s still the same recording even with e.g. different artists credited, then go ahead, but describe it well in the edit note.
  2. There has to be a clear evidence that they are the same recording. That means either:
    • same album, or one is on a box set including the other album or one is on an associated single/EP, …
    • same ISRCs and no contradicting AcoustIDs
    • only matching Acoust IDs, or most AcoustIDs match
    • you have both mediums and confirmed they are the same recording by listening.
    • they have disambiguations that clearly indicate that they are the same (= "live at XY on YYYY-MM-DD - sure there is still the slight chance that the artist played the same song twice at the same concert like Les temps changent on this release).
  3. If 1+2 are a match then its relatively safe that the recordings are the same, but there still might be differences, so if anyone has a plausible concern you should cancel your edit.

What doesn’t count as clear evidence to me (I won’t merge or will abstain):

  • recordings share one AcoustID among many AcoustIDs involved.
  • recordings are on Various Artists compilations (many of those don’t have the correct extra title information so you might be merging clean and explicit versions or a longer and a shorter version that only have 3 seconds of difference. One of the VA compilations might even be a DJ mix and it’s just not marked as such).
  • recordings have the same extra title information (sometimes a remix is more popular than the original and a compilation might have a title called “Song A (radio edit)” when it’s actually the radio edit of the remix.

I am thinking out load so bear with me. This could also apply to the implicit merge, (at the time of recording “add”) , that is when adding a new album either single artist compilation or a Various Artists compilation and it tells you where it came for (or hints where it came from). I have had a number of these and sometimes add as a existing recording (instead of new) if the length is nearly the same, around 3 seconds. Still care needs to be taken to look at the documentation and length. Was I correct or wrong?

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For live there can also be different track splits that can occur where two tracks with same name can have same duration but don’t start and end at the same point.
And also recordings by different persons/sources (audience recorder Bob vs Jane vs mixing console recording, etc.). :smiling_face: