Mark_h and Astromo:
Thank you both for your response.
I tried Astromo's approach first. i.e., I went to the sampler files in my NAS drive, located on the Windows "Network" page and labeled all of the files' Album Artist -- "HDTracks 2013 Sampler." (One file did not have a field for "Album Artist," but I was able to add a field. Then, I went back to MC and requested a manual import run -- which it did. However, all the files were left in the previous condition -- fragmented into several albums, each with its own album art.
I did notice that all the "Album Artist" fields had changed to the new "HDTracks..." terminology. But no unified album was created.
Is it possible that MC saw the old fragmented titles and therefore refused the new import? What else could I be doing wrong? Thanks.