Music, lyrics, both - whatever combination! My choice is 'Moon is up': I guess he is a guy of balance! "the moon is up the sun goes down. You can't have it both ways 'round!"
I say GIMME SHELTER as I remember reading a review that BV did on the Forty Licks Tour. It had to do with being a fan for so long and for some unexplained reason he became almost tearful as he heard the ever-familiar beginning of that song. The story went something like that...if I remember correctly.