Apple Music has become increasingly hostile to user local audio files. What I mean is audio files you create and want to store in Apple Music. Even the interface to manually manage songs is grayed out and doesn’t show you your files that are stored locally in the Finder. In addition, unrealBook only supports locally stored audio files in the iTunes/iPad/iPod library. It always only supported local files, but at some point Apple did or did not support linked cloud files. On iOS12 it certainly doesn’t. On iOS15 it seems like it actually does supported cloud based songs.
For this reason, (years ago) I implemented direct linking of supported audio files (mp3, mp4, wav, aif etc) in the unrealBook documents folder. It’s easy to use. Simply Airdrop, dropbox, open in…. any audio file to unrealBook and it will be imported. After that, use the CD Menu->Music Controller ->link audio file button or CD->menu->play audio file->then + button or create a transmogrify play button and use the use file button to link the audio file.
This is way more reliable, has none of the problems of linked Apple Music and is not subject to any iOS changes to Apple Music.
In short, don’t use Apple Music for linked audio files in unrealBook if you can.
Go to the CD/Music menu and choose Music Controller.
Press Link Audio File (in Blue).
Choose the mp3 (or mp4) song you want to link to the page. You can use the search field to find the file. Press the title to select the song.
Next, go into the CD/Music menu again and choose Player Volume.
Set the slider to the volume you want for this song and then press Set Volume For Page.
Now when you choose this file and turn to the page and press play, the file will play at the predefined volume. Once a volume level has been saved, the window will display the volume level saved with the page.
If you have iTunes library songs, you will need to enable system volume.
Go to settings->global->Playback and enable System volume slider control.
You will be prompted to quit unrealBook. Double-press Home button or swipe up from the bottom to see the multi-tasking card view. Swipe up on unrealBook. Then run unrealBook again.
Now you can set volumes per page for iTunes library linked songs.