MUSICIANS TRENT REZNOR and Atticus Ross are sitting in a studio in Hollywood, staring down the barrel of a rapidly approaching deadline with an air of game fatalism. Their score for David Fincher's new movie, Gone Girl, in theaters October 3, is due the following week. This is their third collaboration with the auteur, and expectations are high: Their first score for 2010's The Social Network netted an Oscar for best original music, and their second effort on 2011's The Girl With the Dragon Tattoo garnered a Golden Globe nod and a Grammy for best soundtrack. Ross, 46, a cerebral London-born composer and producer who...