I ripped files with dbPoweramp to a different drive and folder than I have been using for my rips with J River Media.
I then opened J River and copied the files (Tools>Import) and was able to integrate the imported files into my existing files and play them. I then deleted the files from their original location.
HOWEVER, when I closed down and later came back into JRiver, the files were gone from the JRiver files.
Evidently, the files did not actually copy, but rather only the locations of the files, so that deleting the files eliminated them from my JRiver listing.
Do I have to use Windows Explorer and copy the files to the drive and folder of the other JRiver files, and then do an import/copy from the location to which I had copied the files?