Match to MusicBrainz, adds artwork
Update from Discogs, replace artwork with inferior version to MusicBrainz one because ReplaceAll Set
Replaces Discogs with MusicBrainz
Replaces MusicBrainz with Disocgs
End up with identical Discogs artwork to before run , but because artwork has been changed twice its end up triggering SongSaver to report the file has been modified and hence is resaved and hence shown in SongChanges section and double counts artwork matching in progress bar.