Dalla Guida iTunes MusicBrainz :
Updating Library in iTunes
Brute force method (full library re-scan)
This method works best if
- you've re-tagged a whole lot of your files and don't remember which files/albums
- or there are far too many for the first approach
- or you've moved/renamed files and iTunes has lost them
Ready?
- Go to File > Add Folder to Library
- Point it at the top of your iTunes directory ("My Music\iTunes\iTunes Music\Music" on Windows, by default).
- iTunes will rescan your music, but recognize it's already imported, so you shouldn't end up with duplicate files (unless you have moved/renamed files)
Puoi anche aggiornare una selezione di canzoni seguendo la soluzione basata su AppleScript (nella stessa pagina collegata sopra):
Mac-only advanced method
This method is a bit more complicated to set up, but easy to use.
Fire up Script Editor (which is under Applications/AppleScript, but it will work with TextEdit). Paste the following code, then save as a Script called /Library/iTunes/Scripts/Refresh.scpt (create the Scripts directory if it doesn't already exist).
tell application "iTunes"
refresh selection
end tell
Ora, all'interno di iTunes, dovresti vedere un menu Script (un'icona di una pergamena, a sinistra della Guida). L'elemento "Aggiorna" su quel menu lo costringerà a rileggere i tag per tutte le tracce che hai selezionato.