Why is the album artist field show as blank?

It seems that last night on many tracks the album artist field started showing up as blank when I know for a fact that it is not blank.

I use two tag editors, Mp3Tag and Tag & Rename because both have strengths and I find each useful for different tasks. I know the album artist field is populated on this entire discography because I can see them in Tag & Rename but they do not show in Mp3Tag.

I really have no idea what is happening here because while Mp3Tag does not change the tags until you save them Tag & Rename changes are immediate and I have it set to populate the album artist field if any changes are made to the tags.

Plus, if I click on a track that does not show the album artist in Mp3Tag to play it the album artist field is there in Foobar2000 so this is even stranger.

Any ideas?

So you changed tags in Tag & Rename.

Do you use the library in Mp3tag?
Was Mp3tag restarted after you changed tags in Tag & Rename or did you reload the files you changed or the folder with these files?

Please show us a screenshot of the extended tags dialogue Alt-T for a single file where the album artist is missing.

Here you can see the highlighted track in the track manager section of Mp3Tag shows no album artist but in the pop up window you asked me to show it does.

Thank you.
You see in that dialogue that a field named ALBUM ARTIST has been created. That is a user-defined field.
The correct name would be ALBUMARTIST (one word).
You would have to transfer the data from ALBUM ARTIST to ALBUMARTIST

I didn't create anything LOL...what could have happened? Every thing in the settings shows "Album Artist" in Mp3Tag. I have not changed anything in the settings.

The label of the column does not say anything about the contents.
But you do see in that definition, that a field called %albumartist% is adressed and not %album artist%.
I suspect that somewhere along your tool chain either an action or a different application has created the user-defined field %album artist%.

How would I determine that? Because I have changed nothing in how I do things with tags so if that is so it had to have been done a long time ago. I am organizing a hard drive that has had this music on it for 15 years or longer.

I think you are the only one who can determine that.
How should anybody from the distance find out what you do and what could possibly go in an undesired way?

I could show you a way to get all the data from %album artist% back into %albumartist% - but then you have to find out (yourself) if the field shift happens again and which manipulation you undertook prior to that oberservation.

I know just enough about this to edit the fields "available" in tag editing software. I have no idea how to actually change the fields of the tags and there is no way I did that.

Now it is possible that happened but I did not do it, or do it on purpose. Like I said, these files are 15 years old and I have no idea what software was used to generate or edit the tags all those years ago.

What I am asking you is there a way to take a deeper look at an offending track to see what the fields are labeled and if that has been changed how do I change it back.

There is no way I did this just in the last day because I have no idea what you are talking about. These files were loaded into Mp3Tag and Tag & Rename yesterday for the first time in a very long time.

Mp3Tag is the only software that the album artist of some files does not show. They show in all my other software.

You see the field names in the extended tags dialogue. And these names should be used.
BUT: MP3tag maps the internal representation to the correct fields/atom/chunks/vorbis comments that apply to the different file format. But to get the correct mapping, it would be necessary to find standard obeying names. If that is not found, then a user-defined field is created.

To get back to a way that should be shown also in MP3tag, there are of course several methods:

Load the files without data in ALBUMARTIST
Select all the files.
Use Convert>Tag-Tag for ALBUMARTIST
Format string: %album artist%
Click OK to save the modification.
Keep the files selected, open the extended tags dialogue Alt-T.
You should now see a field called ALBUMARTIST and one called ALBUM ARTIST.
Delete the field ALBUM ARTIST.

If you want to do it in one go, without preview, try an action of the type "Guess value"
Source string: ==%album artist%
Target format string: %album artist%==%albumartist%

That worked but I can only delete the value within the field "album artists". I cannot delete the field itself.

I can only assume these tags were created decades ago but different software than is used now, or maybe could it have been if v.2 tags were created from v.1 tags because I did that a lot 20 years ago?

Did you try that in the extended tags dialogue?

Is that the box you get by ALT-T? Because if so yes I tried it there.

Yes.
In that you find a button with a red X. That deletes the selected field.

It won't. I tried to rename it to just "albumartist" but it created a second field of that name keeping the original "album artist" field, which I was able to delete, but I cannot delete the field "album artist".

Could you supply such a file?

No, because even though when I tried to delete the field it didn't do anything but change the value to "blank" but once I refreshed and then went back to an individual file to send you that field was gone.

I also selected all the files and checked again and that field is no longer present.

So it appears when I run into this I just need to do what I have just done based on your suggestions to get rid of those fields forever and be done with it.

Thank you so much!!

The screenshots show flac files and you mention

Check, if Foobar has the following setting:
grafik