Aw, fsck! I spoke too soon. After all that apparent success with Elisa, I put in my bluetooth earbuds, and tried to select something to listen to in Elisa. But there was nothing there. So I checked the menu again, and the source location was again set to /home/jerry/Misic. And just /home/jerry/Music, where I never keep any music.
So I tried adding /mnt/Music again and again, but every time I close Configure Elisa... and open it again, the library is set back to /home/jerry/Music. It doesn't matter whether I press [Apply] or [OK] after setting the new location, it just doesn't remain set. Once I leave the menu and return, it's reverted.
I have no idea what happened to all that stuff I saw refreshed a while ago. None of it is present anymore.