i have a musician personality theory. ok, it's more like a rock band personality theory. while one could probably peg these personalities onto musicians from viewing a couple music videos, over the years i've noted that this theory holds generally true.

vocalist - token narcissist asshole. too absorbed in their own lives to notice anyone else.
guitarist - mad genius or tries too hard to be cool or combination thereof. tends to be the most creative in the bunch or at least think that they are.
drummer - nicest of the bunch. very easy going and easy to talk to. most likely to be the stablest of the band.
bassist - laid back, generally grounded. personality tends to fall inbetween guitarist and drummer. they have the easy going quality of a drummer, with a touch of guitarist ego as they put themselves out there on the stage and are not hidden by their instrument.
keyboardist - keyboards? there are no stinkin' keyboards in rock music! most likely to be the nerd of the group.

the rarest artist of any art field: endless flow of creativity without ego and elitism getting in the way. in all the arts i think i have only met 1 person like this. it is so rare that you don't realize you have stumbled upon it at first meeting. you may confuse them as the mad genius type or simply mad. upon repeated encounters you notice the humility of their creativity.