rhythmbox never added my music. I thought it might be something wrong with the mp3 plugin, but vlc and the default movie player can play the mp3s. I uninstalled rhythmbox and reinstalled in case it was a discovery issue on startup.
So in desperation, I installed deepin. That does not work either. It now appears that neither one can see my music directory.
I have / mounted on an SSD and /big mounted on a large drive neither program can see the drive.
Sure enough, when I copy to the main drive, rhythmbox can see the files.
There are no special permissions on these files. They are owned by me. How does rhythmbox not work with /big/Music ?