album is split and will not merge in itunes

Select all the album tracks and in Get Info (Command+I, or right-click), add any letter, say X, to one of the main fields (artist name, album artist or album name), then save the changes. If this moved all tracks together, then just repeat Get Info and delete the extra letter.

It seems that making any change in those fields forces iTunes to update tag information, which in turn resolves the issue.

Glad to have been of assistance.

You can report the issue directly to Apple via this link:

http://www.apple.com/feedback/

"It seems that making any change in those fields forces iTunes to update tag information, which in turn resolves the issue."

As far as I can tell the issue is with iTunes' evaluation of its grouping rules that determine how the content of your library is presented to you. I've been able to verify that even when metadata is correct within media files and in the iTunes database (as serialized to the iTunes Library.xml file) albums may still not be grouped correctly in the UI.

The "trick" of appending dummy characters to Artist and/or Album values seems to force iTunes to re-evaluate the grouping rules. This would all appear to be a consequence of a data model in which both Artist and Album are treated as properties of songs/tracks, so iTunes has to "work out" which tracks are associated with an artist and belong to an album every time you open or browse through your library. I suspect that some of this grouping information may be cached in memory to improve performance, and that the "split album" and "multiple entries for the same artist" symptoms may result from a lurking inconsistency in how this cached information is refreshed. All (educated) conjecture, of course - I have no insight into how iTunes actually processes and manages this data 😉

One new tip for really stubborn data. I had three lots of Various Artists in the artists view of my iTunes Match library the other day that wouldn't respond to the usual trailing X treatment. What I found worked was to add the trailing X to start with, but then with each group let iTunes autocomplete from Var... to Various Artists. Picking from the autocomplete lists seemed to work when pasting/editing the whole value didn't.

tt2

It works more consistently if you simply select the songs that should all be in one album and select get info. Enter the correct album name in info and select ok. The songs will all appear in the proper album immediately.