Copyright hypo of the day

Consider the influence of Irving Berlin's White Christmas on Randy Newman's I'm Dreaming and evaluate the potential infringement claims/defenses.  For your consideration: Abilene Music Inc. v. Sony Music Entertainment, Inc., 320 F. Supp. 2d 84 (S.D.N.Y. 2004) (fair use of small portion of "What a Wonderful World") and Newton v. Diamond, 349 F.3d 591 (9th Cir. 2003) (separating out composition and performance elements; Newman's performance allegedly has performance elements that highlight the similarities).  Of course there is the logically prior question of substantial similarity, but for some reason that rarely detains courts in musical quotation cases.