OK, done. The original problem was my albums (folders) were interlaced with individual tracks under Music, making it really hard to scan through 1300+ tracks to find what I was looking for. There were other less important problems too.
I never found the cause that created the problems, but I"m certain it happened while editing tags fields.
To fix it I deleted my libraries, all the MB associated files, and then uninstalled and re-installed MB. Even then, there were very odd things where albums (again folders) did not scan properly. I had to manually re-edit tag data, especially Album. Fortunately, I could edit all the files in an un-named folder associated with one album, then edit the Album field all at once. This happened with about 6 albums.
One other folder did not scan properly. I don't know why. So I removed all the tracks from my library and re-scanned. All the tracks were found, but the titles were gone. So I just re-entered the titles.
All done.
Thanks to all of you who commented.
Dave