There still appears to be an artwork issue for some Music app users. Several Correspondents report that they know they have artwork for a track, or at least are pretty sure that they did prior to updating to macOS 10.15 and the Music app. Some have been able to confirm that a track's file contains image metadata (see Show Me The Metadata). Yet no artwork is displayed for the track in the Music app.
Artwork issues don't fluster me so I hadn't investigated this. But it turns out that I also have some tracks that, despite having files with image metadata, aren't displaying artwork. Not a lot of them and not in every display context (for example, if only one track from an album had artwork, it might display in Album view, and so on). But they were quite noticeable once I started looking for them. A playlist displayed in Playlist View is probably the easiest way to eyeball for them
I tried using the Music app's AppleScript refresh command, which is meant to grab metadata from a track's file, but perhaps it doesn't apply to the image metadata. Anyway, it didn't work to refresh the artwork.
Unfortunately, in this case, Coverscope only works on one track at a time. It wasn't built for batch operations.
So: Apply Embedded Artwork is a script applet I made to refresh a track entry's artwork from the image data already embedded in its file's metadata—image data that is apparently ignored by the Music app.
It can be run on any number of tracks; if a selected track has no local file or already has assigned artwork then it will simply be ignored. If its local file contains image metadata then it will be applied as the track's album artwork.
(My thanks to Correspondent Zak Z. who also confirmed the Coverscope results and beta-tested the remedy.)