Some albums not showing under ‘Artists’ category

This is weird. I synced my music with my Mac earlier as I’d imported a few albums. When I opened my iPod (touch) just now I noticed that under Artists I no longer have The Beatles? The albums appear to be all there if I look under Albums, but nothing listed under Artists. Their stuff is a mixture of CDs I imported years ago and recent downloads from Apple Music Store. They’re not in compilations either. ??