Not sure if I will be helpful, but I find that duplicate albums seem to be seen in N-stream when there is differing meta data. I think this is what Nagoya is referring to with the term 'tags'.
So if you have several songs by an artist, and one song has a different author, or some other differing piece of information in the database of information about that song, N-Stream shows it as a different album. If a song has no album name, it shows as a different album.
For me, it tends to be an issue with songs collected individually, or with my music that I've recorded myself.
I'm using iTunes, Playback and a UnitiQute.
