Q: In iTunes, how can I identify which songs require authorization, which songs were purchased and/or which songs are DRM protected?
A: The simplest way to do this is to create a Smart Playlist to group the tracks that meet your criteria. You can create a new Smart Playlist by choosing New Smart Playlist from the File menu in iTunes and then specifying the criteria you want to match. In iTunes 9, you can specify “Purchased is True” to search for all purchased tracks of any kind, and then filter this with “Media Kind is Music” to limit your Smart Playlist to only music tracks.
The resulting Smart Playlist will contain all music tracks purchased from the iTunes Store. This will include older standard DRM-protected iTunes tracks as well as newer “iTunes Plus” unprotected tracks. If you want to reduce the list to only show DRM-protected tracks, you can easily do this just by adding a criteria of “Kind contains Protected” to match only tracks with the word “Protected” in their kind field.
DRM-protected tracks from the iTunes Store normally have a “Kind” tag of “Protected AAC audio file” while iTunes Plus DRM-free tracks are labelled as “Purchased AAC audio file.” Note that tracks that need to be authorized are the same as DRM-protected tracks, and you only need to authorize your computer once for the iTunes Store account that was used to purchase these tracks. On the other hand, iTunes Plus “Purchased” tracks do not require any authorization for your computer or iPod/iPhone to play them, although your computer will need to be authorized for your iTunes Store account if you ever need to copy these purchased tracks back from an iPod using the “Transfer Purchases” option in iTunes.