Performer credits were already partially entered, and I added the missing ones. Picard has matched it to the correct version. I have both “use track relationships” and “use release relationships” checked in Options. But no matter how many times I ‘Refresh’, the performer tags are missing.
Looking in the debug log, I see that it’s retrieving performer credits:
Just taking a shot in the dark, but have a look under Options -> Metadata and see that you have the “Use release relationships” and “Use track relationships” options checked. If they’re already checked, then I don’t know what to suggest.
Mystery solved - apparently I ripped this CD as MP4 (.m4a) files, although almost all my rips are MP3. As documented in the tag reference, there’s no mapping for performer into MP4 tags. I guess I will go back and re-rip.