That's it really. Apple use a 'persistent' ID for iTune's library, playlists and tracks. At least, in the XML file, but I don't see them listed in the AppleScript dictionary. So:- Are these persistent IDs available to use in AppleScript? What does 'persistent' mean? Obviously I understand what the term 'persistent' means, but in the context of iTunes IDs, just how persistent are they and why have those AND other 'normal' IDs for playlists and tracks. Looking in the Album Artwork folder, I can see numerous persistent library IDs being used, but if it is truly persistent, there really should only be the one, for the library iTunes has always used. When might regular IDs get changed? I know iTunes updates sometimes require a library rebuild. Does that mean they are changing all the normal IDs? I'm looking into creating my own music database and would like a way to link between the 2. Persistent IDs would seem sensible, but iTunes playlists only seem to use regular IDs to link to the tracks. Why would they do that? Anyone shed any light on this?