Q: I have one large playlist that has all the songs I want synced to my iPod Nano. I have another smaller playlist for running to which contains all the songs that are on the one large playlist. Is this unecessarily using up memory space on my iPod? If so, how can I create a sublist from the large playlist so I don’t duplicate songs and use up memory space?
A: As long as you are using automatic synchronization of these selected playlist to your iPod, then the tracks will not be duplicated regardless of how many different playlists they are in, provided that only a single copy exists in the iTunes library itself. If you have duplicate entries in your main iTunes library, then these duplicates may transfer to the iPod as well, since as far as iTunes is concerned, they would be different tracks.
However, for the same track which simply appears in more than one playlist, iTunes recognizes that this track has already been synchronized to the iPod, and doesn’t synchronize it again. In this case, only the playlist entry is synchronized to the iPod, and it references the same track that is in your other playlist, in much the same way that this works in iTunes itself.
Note that if you are transferring content to your iPod manually via drag-and-drop, then copying a second playlist of the same tracks may result in the tracks being duplicated on the iPod. This has been corrected in more recent versions of iTunes, but can still occur under certain circumstances.