It's especially clever for the way it harmonically reworks "Genie" (the original music is in a minor key; "Hard to Explain" is major and has totally different changes), but that's not the point. "Stroke" is a close-up on barely legal Aguilera as she's seduced by what-a-girl-wants Julian Casablancas, who's smiling coolly at her just offscreen. The thrill is in how its details fit together, even though they weren't meant to: the guitar flourish that gooses the beginning of each verse line, the cocksure riff that syncopates her "oh-oh-oh." Hooked by the Strokes' drum turnaround, "come come come on and let me out" sounds like they're locking eyes. Without changing a word, "Stroke" recasts the subtext of "Genie" from "play your cards right and you might get lucky" to "I can't talk myself out of this, but I might regret it."

Other "voice from song A/music from song B" mixes are cluttering shared folders everywhere: "Bootylicious" + "Smells Like Teen Spirit," "Get Ur Freak On" + "Faith," thesis + antithesis, fun to hear once. "Genius," though, follows through on its boast of synthesis. It's cooler and sexier and tenser than either of its sources, and it makes me want more. There are no other records that sound like it right now: nothing else with the high-budget precision songcraft and high-definition poptones of Christina that also rocks, nothing else with the skinny hips and sharp teeth of the Strokes that understands the pleasures of TRL. Each is what the other one was missing all along.