I've been going through the different threads and this seems the closest solution (maybe). I'm not quite understanding how one could change the cover's description in a batch.
Is it actually possible to take the title and artist and create a new description?
The description is a fixed string and no format string.
This means: only real words, no variables or scripting functions.
Or in other words: the string is not dynamic and creates the contents from other sources like tag fields
How would I change the cover's description on 100 files in one go?
I just tried 10 files, did a right mouse click over the cover and used "Set cover description. After it asked me if I wanted to save, which I did. The original text is the same.
I bet you have, esp. if you look at the little word
Please check out the toolbar for "Actions (quick)" and also follow the linked description of action if you do not feel comfortable with the action alone.