👓 ‘Hard Day’s Night’: A Mathematical Mystery Tour | NPR

Read 'Hard Day's Night': A Mathematical Mystery Tour (NPR | Weekend Edition Saturday)

The jangly opening chord of The Beatles' hit "A Hard Day's Night" is one of the most recognizable in pop music. Maybe it sounds like nothing more than a guitarist telling his bandmates, "Hey, we're doing a song here, so listen up." But for decades, guitarists have puzzled over exactly how that chord was played.