Square Enix recently made the soundtracks to every main Final Fantasy game available to listen on Apple Music and Spotify (via TechCrunch). The release of the soundtracks on streaming services is being timed with a special concert for Final Fantasy VII that's taking place this week in Hollywood.
To find the music, head to Apple Music and search for "Final Fantasy original soundtrack." In the results for albums you can tap "See All" to discover soundtracks for original games in the series like Final Fantasy and Final Fantasy II, and even modern entries like Final Fantasy XIII and Final Fantasy XV.
As pointed out by TechCrunch, there are some missing entries, including soundtracks for Final Fantasy X-2, Final Fantasy Tactics Advance, and Final Fantasy Tactics A2: Grimoire of the Rift. Otherwise, every mainline entry in the franchise now has its soundtrack ready for streaming on Apple Music, from Final Fantasy I to Final Fantasy XV.