“Aperture” isn’t a disco song. Produced by Kid Harpoon, it’s subtler, propelled by three thumps and a syncopated fourth beat, double-timed by electronic buzzes and bursts of assorted percussion that mount up and then dissipate. Above that pulse, Styles croons vague lyrics on the way to a big choral affirmation — “We belong together” — only to immediately undercut it: “It finally appears it’s only love.” Ambivalence reigns.