Billy Strayhorn wrote Multicolored Blue. Billy to me is the boss of the arrangers.
I mean, I don't think I would call Claus to do an album of big band tunes. You know, just like arrangers write for the artist they have in mind; you have to keep in mind if you're going to work with Claus Ogerman. You invite him to do what he does.
I fool around with guitar and I can fool around on piano. I don't really play either instrument although I can play a couple of songs on guitar. You don't really need to be able to play to compose. There are many composers and arrangers who work out of their heads.