On July 5, 1954, Elvis Presley walked into Sam Phillips’ Sun Studios in Memphis and invented rock and roll. The moment when Presley, 19, guitarist Scotty Moore and bassist Bill Black first started messing around with Arthur (Big Boy) Crudup’s “That’s All Right”—making it faster, more exuberant—is captured here, and it still sounds audacious, as if the players themselves can’t believe what they’re doing. The same originality animates “Good Rockin’ Tonight,” “Blue Moon of Kentucky” and “Mystery Train,” and makes a lot of the work Elvis did later seem, if not superfluous, at least a little dull.