Matching the young-adult tumult of Kelly Clarkson with the wind-swept angst of Florence and the Machine, Perri's 2010 smash hit "Jar of Hearts" was bad-boyfriend-crushing piano pop — the kind of thing that you crank as you decide which local cliff to jump off when your high school love dumps you for a Cheerio. Her newest blast of feelings-napalm is a ballad that starts out placid and folky, then picks up intensity and volume, as grand melodic swooshes (and timpani!) imply romantic rapture between Perri and her new man. But watch out: Chrissy's valentine seems to come with a razor blade of crazy: "I can't make you bleed if I'm alone." Dude, run.

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“I'm Yours”

Jason Mraz re-emerged after his disappointing second album with this lead single, a Jack Johnson-esque ditty about giving yourself fully to someone else. The success of the reggae-tinged song (it earned two Grammy nods and a spot on the Billboard singles chart for well over a year) was something the folk-pop singer never predicted when he wrote it in 15 minutes at home. "I played a happy-hippie chord progression that would probably work without 50 different Bob Marley songs," he told Rolling Stone. "I thought, 'It's too novelty. This is a nursery rhyme,'" concluding that "you can never guess what's gonna be a hit."