(Or: the perennial headache of music library software writers!)

Computer music libraries are, typically, made up of audio files, one per musical track. When applied to musical albums the software you use (including Astiga) must work out how the tracks are grouped.

Each audio file in a library can be tagged, whereby identifiers, classifiers and structural/positional information is recorded in the file. For example, the name of a track, who sang on it, its surrounding album and its track position within that album, and much, much more.

Each audio file is also located with a path, that is, the folder and filename of the audio file. For example, /Music/The Beatles/Revolver/1-Taxman.flac.

This article explains how Astiga groups tracks into albums and what you can change in your own files if an album is not grouped the way you expect.

Astiga never sees an album, only tracks

There are no explicit, deterministic means by which an album is created, identified or structured. There are only audio files, sitting in folders, each with information about itself (“metadata”, otherwise known as “tags”). When Astiga “synchronises” your storage with your Astiga library it reads those tags from every file it finds, and then uses that, along with the location of the file in a folder structure, to suggest which files belong together in albums.

Because the answer is worked out at synchronisation time rather than stored, it can change. If you retag your files or move them around, the next scan may change the album grouping.

The tags that matter

Four pieces of information decide which album a track lands on, and what that album is called:

• the album title tag
• the album artist tag — sometimes shown by tagging software as “band” or “ensemble”
• the artist tag, which is the artist of that one track
• the folder the file sits in

The track title, track number, disc number, year and artwork are all read too, but they do not affect the grouping; they are used for album-level information such as album art, year of release and more.

Rule one: the album title decides what can be grouped

Astiga will never put two tracks on the same album if their album titles differ. “Abbey Road” and “Abbey Road (Remastered)” are two albums, and so are “Vol. 2” and “Volume 2”. Any difference in the words or punctuation counts.

Three kinds of difference do not count: capitalisation (“Kind of Blue” and “Kind Of Blue” are the same album), accented (diacritical) characters (“Cafe del Mar” and “Café del Mar” are the same album), spaces at the end (not start) of the title, and allographs or composed characters e.g. ‘Straße’ = ‘Strasse’. Titles that differ only in these ways are the same album. Note, however, that one of the variations will be chosen, and it might not be the one you prefer.

This is the one rule with no exceptions.

A track with no album title is not on any album at all. It is still in your library and still playable (you will find it by artist, on the Songs page, or by searching) but it will not appear in the album list.

Rule two: the folder decides how tracks sharing a title are divided

Sharing a title is not always enough. Plenty of libraries hold several different albums called “Greatest Hits”, or the same album twice at different qualities. Among all the tracks that share an album title, Astiga looks at the file path structure (the name of the file and its parent folders) and groups them bearing in mind the files’ containment.

A few consequences worth knowing:

• Two albums with the same title in unrelated folders, neither sitting within the same grandparent folder and not side by side under the same parent folder, stay two albums.
• Two same-titled albums in folders under the same parent folder will usually come out as one album. Keeping them apart needs different titles, or album artist tags that disagree strongly enough to split them.
• The same album stored twice, in unrelated folders, will show up twice.
• A multi-disc album split into “Disc 1” and “Disc 2” subfolders is treated as one album, because Astiga looks at the folder those subfolders sit inside.
• If all your music sits in one flat folder, the folder tells Astiga nothing, and everything sharing an album title becomes one album.

Rule three: the album is named from its tracks

Once Astiga knows which tracks form an album, it decides who the album is by. It asks three questions in order and stops at the first one that gives an answer.

Does more than half of the album carry the same album artist tag? If so, that is the album artist. This is why the album artist tag is worth filling in: it is the strongest thing you can say about an album, and it survives everything else. An album by one artist with a couple of guest features stays under that artist.

Otherwise, does more than half of the album carry the same artist tag? If so, that becomes the album artist. This is what happens on a well-tagged album by a single artist that has no album artist tags at all.

Otherwise the album is a compilation, and Astiga names it “Various Artists”. Twenty tracks by twenty different artists give no majority to anyone, which is exactly right for a compilation.

There is one last case. If not a single track on the album carries any artist information at all, Astiga leaves the album artist blank rather than calling it “Various Artists” — “Various Artists” means your tracks disagree about who the artist is, and these ones simply are not saying.

A stray tag does not break up an album

A common occurrence is that the tracks in an album can have an odd track or two with different tags from the rest of its album. For example: a compilation where one track came from somewhere else and carries an album artist tag naming one performer.

That track stays with the others inside the same album, and it does not override the naming or album-level artist attribution. Astiga is looking for quoracy, so a single tag among twenty is outvoted.

The same works the other way: a track missing its artist tag altogether still joins its album. Missing information is not a reason to leave a track out when the other evidence is strong that it should remain in.

Tags can break an album up when there is genuine disagreement amongst enough members. If more than half of an album’s tracks carry album artist tags and the tags point at two or more different artists with no clear winner then Astiga treats them as two separate albums. A strong majority is different on an album with more than four tracks: one artist tagged on roughtly two-thirds of all tracks is one album with a guest credit, not two.

The other things an album shows

An album’s year, its decade and its cover art also come from the tracks on it:

• the year shown is the latest year among the album’s tracks;
• the decade is derived from the latest stated year among the album’s tracks;
• the artwork is taken from the embedded art inside tracks and from co-located files within the same folder as any one of the files.

It does not matter which track was scanned first. Two people with identical files, scanned in different orders, get identical albums.

When albums are worked out

Astiga regroups your albums at the end of each synchronisation of your storage (but only when sync has made a change), and again straight away if you edit a track’s tags in Astiga itself. You do not need to do anything to trigger it, and there is no separate “rebuild” step for album membership in isolation.

If you retag files in your own tagging software, the change reaches Astiga on the next sync.

Fixing an album that is grouped wrongly

Almost every grouping complaint comes down to one of the rules above. In rough order of how often they are the cause:

An album has split in two. The album titles are not identical or they are spread too widely across the file structure.

• Check for differences in wording or punctuation, such as “Vol. 2” against “Volume 2”.
• Check for extra information such as “(Remastered)” on one set of tracks.
• Check the tracks are not in entirely unrelated folders, sharing no parentage — see rule two. Consolidate the files together.

Capitalisation, accents and spaces at the end do not matter.

Two different albums have merged into one. They share an album title, and their folders sit close together.

• Give them different titles
• Move the files so they neither share a parent folder nor sit inside one another.

An album is under the wrong artist.

• Set the album artist tag on every track of that album.

An album’s capitalisation, punctuation or diacritization is incorrect. At least one of the tracks has this non-conforming form.

• Set the album tag to be consistent.

An album by one artist has become “Various Artists”. The individual artist tags disagree, often because guest performers have been written into the artist tag on some tracks.

• Set the album artist tag consistently on all of them.

A compilation is under one performer’s name. More than half its tracks carry that name in the album artist tag.

• Clear the album artist tag from those tracks or set it to “Various Artists” on every track.

Two same-named albums have appeared, split by artist. More than half the tracks carry album artist tags, and the tags disagree with no clear winner.

• Make the album artist tags agree to put them back together.

A track is missing from the album list entirely. It has no album title tag.

• Tag the missing album name.