Building playlists On one level, building playlists isn’t very complicated at all—use the three-dot menu or a right-click to add albums or tracks to playlists, mixing Apple Music picks with tracks from your local library as much as you want.
Dive in and play anything from Apple Music, straight from Apple Music, and your local library will remain untouched—those Artists, Albums and Songs links down the left-hand side of the Music app interface won’t suddenly be populated by everything you play on the streaming service.
As well as giving you access to however many millions of tracks over its streaming service, Apple Music also lets you mark albums and artists and songs as part of your library—a curated little corner of Apple Music to help you to get back to your favorite tracks more easily (via the artist or album links, for example), and to sync them between devices.
This guide is an overview of how you can use the Music app on macOS to combine both a local library of imported digital tracks (MP3 or otherwise), and a catalog of tens of millions of streaming songs.
Turning off this option is a good way to keep your local files and Apple Music at least partially separate: You can mix both streamed and local tracks together in playlists, but your main library has just the stuff you’ve specifically added (the playlist tracks won’t show up in the Artists, Albums and Songs sections).