Album Artist shows in iTunes but blank in Mp3Tag

[ohrenkino]

How did iTunes get the album artist?
In the old days one could force iTunes to write the database data to tags by changing the tag version - also from V2.3 to V2.3 so that no data was lost.
Perhaps this would be the first step: fill the empty tag fields with the existing data.
Also, you could check whether you have APE tags in the files and then see whether you read them and what happens if you don't.

Then, to copy one field to another, see

Actions and batch-operations

How to copy one field value to another field? Example how to copy the content of the ARTIST field to the ALBUMARTIST field: Create a new action in an existing action group or make a new action group. Action type: Format value Field: ALBUMARTIST Format string: %artist% Note: If you want to copy all possible values of a field (in case you have multiple artist fields), the internal scripting function $meta_sep can be used in the format string, e.g., $meta_sep(artist,\\\\)