Lyrically, Adele leans on a familiar kind of outrage, reckoning with a lover who broke every promise he ever made to her. The song opens with carefully plucked acoustic guitar, and when the chorus comes in it’s as if someone yanked the curtains up on a dark room. 'Send-my-love/ To-your-new/ Luh-uh-ver.' The results are like encountering a person with perfectly symmetrical features-both instantly appealing and deeply, existentially unsettling. To that end, Martin is as exacting of a songwriter as I’ve ever heard: like he did with the tracks he made for Taylor Swift ('Shake It Off', 'Blank Space', 'Style') and Katy Perry ('I Kissed a Girl', 'Teenage Dream', 'Roar'), he relies on some enigmatic internal cadence, clipping syllables like a hiccuping poet, taking a tiny scalpel to his melodies. Stack ‘em up, and all of Martin’s songs follow a particular formula: they’re prickly, quick-moving affairs that braid the precision of Swedish pop like ABBA with the more groove-oriented rhythms of American R&B. Or: 'We both know we ain’t kids no more,' which is how she puts it on 'Send My Love (To Your New Lover)', a song co-written by Max Martin, the 44-year-old Swedish super-producer who has now penned almost as many number one singles as Lennon and McCartney.

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