I think there are 7 kinds of music. But each of us has to define those categories for ourselves (I'm guessing here that after 7 the categories become derivitive). But, having said that there may actually on be 2 kinds of music: a song is either a love song or it's not. Songs that are not "love songs" are about things like death, enlightenment, nature, and work. Love songs are about things that happen in the heart because of another person who you either can't have or don't want (or are in the process of moving from one of these states to the other). Or they are celebratory -- hooting about him or her and how wonderful it is that you are togther. So what's the greatest love song every written? Good grief, how does one decide. Did it make you cry? That's a pretty good indication that it at least got to you. Oddly, Samual Barber's and Albinoni's adagios and the slow moment of Mahler's 5th are right up there in my book. Snow Patrol's Eyes Open is a whole CD full of love songs. And don't forget Set 'Em Up Joe!