If you have a Pro subscription, you can add music from your own library to your mashes.
On iOS
To do so, follow the usual steps to add music, but tap on My Music instead of a 1SE track. The first time, 1SE asks for access to your music library; tap Allow. A music picker then opens inside 1SE, showing your library by playlists, artists, albums and songs.
Songs protected by digital rights management (DRM) can't be used in a mash.
DRM means that you cannot use music you don't own, for example, music from your Library that you have downloaded using an Apple Music subscription. You'll need to purchase and download the song from the iTunes Store to use it in your mashes—you can't use music stored on iCloud.
On Android
Follow the usual steps to add music, but tap My Music instead of a 1SE track. 1SE asks Android for any audio file, so which app opens depends on your phone—usually the Files app, though some devices show their own sound picker that lists your music. Any audio file works, not only .mp3.
The picker often opens on Recent, which can be empty even if you have music on the phone. If it is, browse to the folder your music is in and pick the track from there.
