Sorry for the late response. Unfortunately I had a huge project I had to focus on and could not break away. Thank you for the very detailed explanation. I knew all of that already, but hopefully it will benefit another because it was extrremely clear and well-written. Unfortunately, I cannot reproduce what was happening before. I haave forgotten some of the variables as it took so long for anyone to respond. I am sure it will come up again as I keep working on this project.
Basically what I am trying to accomplish is to repurpose the Artist Sort and the Album Artist Sort fields to list the Main Artist (Album Artist Sort) and to list all participating artists (Artist Sort).
Since itunes does not have a field for all participating artists, I had to do this work around. I would use a custom field that itunes does not use to store that information, but I want to be able to use that information to create smart playlists. So I can tell the smart playlist to search to the artist name in the Artist Sort field and I can make a playlist with all songs that artist participated in, not just those they were the main Artist or Album Artist. For example, if I wanted make a playlist with every song Jerry Garcia played in, I would also get Teach Your Children by CSN, as I listed Jerry Garcia in the Artist Sort field, even though he was not the Album Artist (CSN) or the Artist (CSN). Of course I could add in the Artist field "with Jerry Garcia," but I cannot do that for all the people playing in the song.
The Main Artist is different from the album artist in my custom Style Guide. I use the Main Artist to group all songs I want to fall under that artist. For example, there are the Verve Master Recordings for Charlie Parker. The Album Artist would be Charlie Parker, but in that album there are songs that appear in Milestones, by Miles Davis. To keep the Album together in iTunes, I MUST use one artist and in this case in makes most sense to use Charlie Parker (rather Parker, Charlie) but those songs are Miles Davis songs so I use the Main Artist (which is the Album Artist Sort field, repurposed) to group those songs under Miles Davis.
To summarize, I have repurpose the fields (Except for Artist, which functions as intended in iTunes) as such:
-Album Artist: used to group all songs in an album together
-Album Artist Sort: used to group all songs by an Artist(s)/Group together
-Artist: Used to List Main Artist(s)/Group for an individual Song. I don't really use this for sorting but rather as an informational tool.
-Artist Sort: Used to list All Artists involved in the recording. Again, not used for sorting, but to contain information to be used by smart playlist and the curious listener.
Because I am repurposing these fields I need them to sort individually and not affect each other, unless with the aforementioned case where one field is left bank. I understand how that affects things as you so well explained it. I read an article that stated that even if you sorted by Album Artist (with the field in bold), the songs would still sort by the values in the Album Artist Sort field. I wanted to make sure that was not the case, so I started sorting with different test values in the fields and they were not sorting in the proper way. They are now, so I need to keep testing so I can reporduce the prople, produce screenshots and report back. If I don't experience this again in the next month I will report back that it seemed to be a bug or perhaps some sort of user error, but I don't think it was.
I just wanted to report back to give some explanation to what I was trying to do to give the matter some relevance.