In Apple music songs can be in three^ states: Null, In Your Library, or Downloaded, with downloaded being a subset of “In your Library”. When you are offline you can look through all your library and see those songs which you’ve added but not downloaded as greyed out, versus the download ones as black. There’s also a view that filters the library so it only shows downloaded. If you click a black Downloaded song, it plays, if you click a grey In Your Library one, it says “Connect to Data to play this song” or similar.

^ I lied, there’s actually a fourth hidden state “Cached” that the UI presents as “In your Library” rather than “Downloaded”, and will give the same “Connect to data…” error if you directly click on it to play while offline. However, if you click Play on the album/playlist/etc itself, you can then navigate via the “Next Button” and “Up Next” queue to pick the song and if you played it recently, it’ll work. Great if find yourself in a plane and there are some songs you’ve been listening to lately but forgot to download.

I’ve been meaning to write a blog on “The Hidden Cache Apple Music Doesn’t Want You To Know About” for some time now lol. But knowing Apple I’d half-expect them to “patch the bug” by preventing the hidden cache from being played offline.

Apple Music has a "Downloaded" browsing section (along with Artists, Albums, Composers, Genres, etc) that you can browse and search separately. Works fine.

But isn't that the whole point of UX engineering? Liked songs is also "just a playlist" but by adding a unique icon for it now you can add it with one tap, filter artists that you like the most, and when you go to an artist's page it can show all the songs by that artist that you've liked.

I think you can create such a playlist. I did that (I called it "on the road" for exactly that purpose) and every time I add a song it's downloaded immediately. Unless they changed something.

But yeah in general I agree that Spotify UX is less than optimal.