Schinckel.net

This seems to be pretty new in iTunes (i.e., I haven’t noticed it before): if you are viewing an album in the grouped view, and you have ratings on some or all of the tracks, it displays an average rating for the album:

This is in a different set of stars to the normal rating of tracks. However, you can explicitly rate an album too, which changes it to the other type of stars:

Interestingly, if you do this to an album with tracks already rated, it will choose ratings for the tracks that haven’t been rated, so that it creates the right total rating:

This rating isn’t stored with the track, if you open the Info window for one of the hollow star rated tracks, it hasn’t actually been rated.

This is quite interesting.