Deleting songs from iTunes library
If you find a song on one of your iTunes playlists you no longer want, you usually have to go all the way back to the “Music” view and find it to delete it. This shortcut saves you the trouble, eliminating the element directly from the playlist view.
Normally, pressing the Delete key while on a playlist, only prompts you to remove the song from the playlist. If you want to completely remove it from your library, simply press Shift + Delete (Windows) or Option + Delete (on OS X), and get the message to delete the song from your library completely. Very convenient for us addicts playlist.