Cut Apple Music iPhone Storage Usage in Minutes – Here's How
As an Apple Music subscriber, you're able to download songs, playlists, and albums from the Apple Music catalog to your iPhone or iPad for offline listening, but this can gradually eat up your devi...

Source: MacRumors
As an Apple Music subscriber, you're able to download songs, playlists, and albums from the Apple Music catalog to your iPhone or iPad for offline listening, but this can gradually eat up your device's storage space over time. Fortunately the Music app includes a handy feature that can spring into action whenever your device's storage space runs low, and automatically offload songs you haven't played for a while in order to make space for newer ones.