I used ITunes to download to my new IPad3 a variety of songs and albums I had already purchased. However, in some cases, I have two copies of every song. When I play an album with the "Music" app, I can see two copies of each song - and yes it plays both copies as it moves forward.
I've seen instructions online of how to get rid of ITunes duplicates on a PC. But I'm dealing with my IPad3, not a PC.