Music downloading- where did my albums go?

[Norman Lidbury]

I downloaded one of my albums earlier today via windows media player, synching to the nexus. Ok so far. This evening, I tried to synch another 2 albums. Whilst the first one has appeared in the music widget with it's cover, there is no sign of the other two. Opening up the file structure of nexus on my computor, the music is there, in Nexus 10/internal storage/music/album name. However, when looking in storage, this afternoons album is there, but not the other two. They're definitely in there somewhere- how do I get them to function?
Norman