Her ascent has been gradual, but Kelly is "right on the verge of breaking wide open," says Sharon Dastur, iHeartMedia's senior vice president of programming integration. And with a résumé of her caliber, it's easy to see why: After a brief stint on American Idol in 2010 (she was cut before the semi-finals), the 22-year-old posted a silvery acoustic cover of Frank Ocean's Thinkin' Bout You on YouTube in January 2012, which now accounts for 21 million of more than 85 million views she's accumulated on the site. Like other Internet sensations Justin Bieber and Carly Rae Jepsen before her, the honey-voiced singer-songwriter was scooped up by manager Scooter Braun, and has since opened shows for Ed Sheeran, Sam Smith and Jewel this past year and a half. With two EPs under her belt (last year's Foreword debuted at No. 16 on the Billboard 200 albums chart), the Southern California native is now prepping her debut album for release in 2015, led by a Max Martin-produced single early in the year. – Ryan