NSDictionary 😉
Location of the iTunes Music Library file is nearly always ~/Music/iTunes/iTunes Music Library.xml.
To load this:
[NSDictionary dictionaryWithContentsOfFile:[@"~/Music/iTunes/iTunes Music Library.xml" stringByExpandingTildeInPath]];
Open the xml file in property list editor to see the layout, but the main keys that you will want are "Tracks" and "Playlists".