Thanks, phred. I am familiar with the concepts you mentioned. My question was prompted by my observations that, when I copied my music files from one location to another, not all album-art photos showed up in the destination location - which surprised me because I thought that, once embedded in the music file, every photo would move with the files.
I have been able to recover those missing photos by repeating the copy process, after first removing all associated library files from the destination location, then recreating the library after completing the copying process. I am still learning the little eccentricities of getting the most out of MusicBee and making it behave in accordance with my desires.
Best,
Art