For anyone who's already screaming "Enough!" whenever Avril Lavigne's supernaturally catchy single "Complicated" comes on the radio, the news is all bad. Let Go, the debut album from Ontario's tiny terror, comes fully loaded with another dozen infectious hymns of Total Request angst. Although it's the only track with a definable style other than "pop rock," "Sk8er Boi" is seventeen-year-old Lavigne's signature moment. Over a rush of nouveau-punk guitar chords, she narrates a funny story line (preppy ho disses young scofflaw, who then becomes MTV star and — psych! — Avril's boyfriend!), but none of it would matter if Lavigne didn't have a voice, equal parts baby girl and husky siren, that seems capable of setting off car alarms several city blocks away. "Mobile" should be her next completely inescapable hit: As Lavigne wails over crashing waves of acoustic and electric guitars, her big voice occasionally turns sideways in a drawl, a casual hint that she may actually be, of all things, a fine country singer in the making. Truth be told, Lavigne has a great voice, a good shtick and a qualified staff of hitmakers. We should all just learn to get along with her, because she's gonna be with us for a little while.

“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."