What do "Needs Review" and "Review Alternates" mean in Apple Music?

Quick answer

They mean Apple Music couldn't find an exact match for some songs, but it found similar versions you can choose instead. You have 30 days from the first transfer to review them.

When a transfer ends with Some Music Needs Review, everything that matched cleanly is already in your library. The leftovers are songs where Apple only found an alternate, like a remaster, a live take or a different release of the same track. Review Alternates opens the list so you can pick the version you want and save it, according to Apple's transfer guide.

You have to review on the same device that started the transfer:

• iPhone or iPad: Settings, then Apps, then Music, then Review Current Transfer.
• Android: More, then Settings, then Review Current Transfer.
• Web: click your photo or monogram, then Review.

Two things catch people out. First, the 30-day window: after that, those songs aren't added. Second, you can't start a new transfer on that device while a review is still waiting, so clear it before moving your next batch.

If an alternate is wrong, skip it and search Apple Music for the song by hand. For songs with no alternate at all, the track probably isn't in Apple's catalog in your country.