How iTunes remembers audio CDs
If you burn an audio CD at home, iTunes on your computer will see it differently than iTunes elsewhere. Read on to understand why.
First, a few words about the Gracenote Media Database
The Gracenote Media Database is a service that provides album names, song titles, and other information about audio CDs. iTunes connects to this database to look up information about the CDs you own so you can easily select which songs to listen to and sort and view your music library.
For more information about the Gracenote Media Database, visit the Gracenote website.
Remembering purchased audio CDs
When you insert a store-bought audio CD into your computer, iTunes goes online to the Gracenote Media Database and finds the CD and track names based on the lengths of each track and the overall length of the CD.
Each time you reinsert that CD into the same computer while logged in as the same user, iTunes will "remember" the information without having to look it up on the Internet again.
Remembering audio CDs you burn
iTunes also "remembers" every audio CD you burn. However, the CD and track names are not burned onto the CD itself. If you insert the burned audio CD into another computer, or even log in as another user, the CD will be titled "Audio CD", and will have generic track names. Since the track length and the overall CD length is the same as the store-bought album, iTunes finds the information for the store-bought album when it looks the CD up online.
Remembering CD information you enter manually
If you enter a CD's track names manually, iTunes imports the CD and saves this information. This is helpful if you enter information for a CD that is different than what you inserted. If you have not imported, it allows you to eject and reinsert to undo all of your entries.