Bruji

iTunes has a Grouping tag. Its official use is this: group related tracks of a piece of music (a "work") which spans multiple tracks, like all of the movements in a concerto. Grouping is a classification level higher than song or track, but lower than album or disc.

For example.

Dmitry Shostakovich
Symphony No. 7 "Leningrad"

Allegretto
Moderato (poco allegretto)
Adagio
Allegro non troppo

"Allegretto" et al are the Tracks, while "Symphony ..." is the Group.

Metal fans may recall Fates Warning's "The Ivory Gate of Dreams" and Symphony X's "The Odyssey", which have the same structure.

A Track Group in CDpedia has several characteristics:

1) Ordinarily, the sum of the durations of the grouped tracks is displayed. This sum is not editable. If none of the grouped tracks have durations, which generally occurs because they're joined into a single track and it's too much of a pain to figure out the durations of the individual movements within the work, the Duration of the Group becomes editable.

2) When matching to iTunes, there are two scenarios to look for when matching tracks and designating an album with a "two-leg" note.

2a) If the Grouping tag is missing in iTunes, but there is a single track with the same name as the Group's, as often occurs when the work has been joined into a single track, that constitutes a complete match for the Group and its tracks, and may qualify the album for a "two-leg" note.

2b) If the Grouping tag exists in iTunes, then the Tracks are matched individually, and the Group is not matched against a track. If all the individual tracks exist, then the Grouping is marked as "good" and the album may qualify for a "two-leg" note.

3) Track numbering for a Track Group has a Separator, a Scheme (Alphabetic, Numeric, Roman Numeral), and a Starting Letter/Number. For example, if the Group is "track" 8, the separator is "-", the Scheme is Numeric, and the Starting Number is 56, the tracks would be numbered "8-56", "8-57", etc. If the separator is blank, the Scheme is Alphabetic, and the Starting Letter is blank, the tracks would be numbered "8a", "8b", etc. You can set the Starting Letter to "A" if you want "8A", "8B", etc. It's simpler if this is global for all Track Groups, rather than individually settable for each Track Group.

4) You can select if tracks are hidden by default in the Info pane, and only the Group's name is seen. Editing (Apple-E) an album always shows all tracks. That means if hiding is turned on the user must Edit in order to see the individual tracks, but that's easier than adding a hide/unhide element to the UI.

5) A Group is designated in the Editing pane just like Artist and Composer are.

Thank you for the feedback. As you know CDpedia currently uses a much simpler system that would not allow for such a complex matching. Looking to the future could you please email us an XML export of a playlist in iTunes containing some of these groupings so that we can have something to test against and refer to if we try to implement this feature. You will find the export command in iTunes under the file menu Library --> Export Playlist.

I was thinking you could simplify this idea and dump the iTunes matching bit without losing any real functionality.

1) Any contiguous set of tracks with the same non-empty Group field constitute a Group. The degenerate case of a single track is A-OK.
2) Tracks in a group are sub-numbered (8a, 8b, etc). The numbering scheme I described is complex, but ultimately flexible. I'd understand if you went for the simple solution.
3) In Preferences, you can opt to "Display Groups instead of Tracks" in the Info pane. Some sort of visual indication you're seeing a Group and not a Track would be ideal. The Duration displayed in the Tracks subpanel of the Info pane would be the sum of the Durations of the Group's tracks.
4) In Preferences, you can opt to "Ignore missing tracks in Groups". When you do a "Refresh iTunes Tracks", this means that a missing track that's part of a Group doesn't count against the album when deciding whether it qualifies for a two-leg note designation.