Silent
Available only in Alarm-specific settings. Won’t turn off vibrations.
Single ringtone
You can choose a single ringtone or multiple ringtones to create a playlist (see below).
Playlist
Tap on the playlist icon in top right and choose files to create your own playlist.
Browse your local files
Tap on the folder icon and select your files from your internal or external storage. The system file picker will show up and you may need to enable external storage access first before you can see it in the picker.
Spotify playlist
You can add your saved albums or playlists from Spotify’s Your Library > Albums / Playlists
Other playlists (including Google Play Music playlists)
Lots of media player apps can create such playlists from music that is available on your phone.
File-based playlists
You can use any file-based playlist (.m3u, .pls) you have on your phone.
This is a companion discussion topic for the original entry at https://docs.sleep.urbandroid.org//alarms/ringtone.html