Quora: How big of a library can iTunes handle?
‘For most people today (9/27/2011) running a typical system, try not to go over 30,000 songs if you value the user experience. There is no doubt this will not be an issue in the future.’
Moody
Tags music in iTunes on a grid of Calm - Intense, Sad - Happy.
codepoetry: Do-It-Yourself Smart Radio Station
Using iTunes' Smart Playlists to make a great radio station with Party Shuffle.