How would you sort Ayu's music?

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Well, I've been reading about how people use the grouping tag in iTunes and I discovered that it would come in really handy when sorting Ayu's music, like her rock songs, ballads, etc. My question is: how would you sort Ayu's music? I really want to make some kick-ass playlists, but I'm having trouble sorting her music.

Examples
JEWEL- winter soft piano ballad
momentum - winter ballad
Together When - winter ballad
Beautiful Fighters - happy pop
BLUE BIRD - summer pop
Marionette - dark rock ballad? (slow at the beginning)
criminal - dark rock ballad? (also slow at the beginning)
GUILTY - dark rock ballad?
glitter - happy summer pop
fairyland - summer pop
my name's WOMEN - pop rock?