Back in January, Duke University student and Detroit native Mike Posner -- who's spent the last five years writing and producing for other artists -- made the impulsive decision to hole up in his bedroom and finish up a mixtape.

"Somewhere along the way I realized that the stuff I was writing and trying to give to other people just didn't fit with them. Nobody could pull off the lyrics that I was writing except me," he says.

Knowing his prospective audience wasn't the Z-sharing demographic, 21-year-old Posner opted for a more familiar means of distribution: offering the album as a free download on iTunes. "I just tried to put my music in the most accessible place ever," he says. His plan succeeded quickly: in just two months, his album, "A Matter of Time," reached No. 1 on iTunesU. Soon after, he hooked up with manager Dan Weisman of Elitaste, and in June he inked a deal with J Records and Sony/ATV.

"Mike is an anomaly," says one of his agents, Alex Kirshbaum of NUE Agency. "In a matter of months, he's gone from recording in his dorm room to playing sold-out shows across the country, and the crowds are singing along to every word of his songs."

Posner describes his sound as "pop without guilt," but his influences are very eclectic - Charlie Parker, Rage Against the Machine, Paul Simon and Talib Kweli each take up pages of his CD-case. Though his first mixtape saw him as the singer, songwriter, producer, and arranger, for his as-yet-titled major label debut he's working with such producers as Benny Blanco and Sam Hollander, with the album slated for a 2010 release.

On Oct. 29, his second mixtape, "One Foot Out the Door," will be available on iTunes for free, and features collaborations with Kid Cudi, Wale, 3OH!3, Bun B, and Big Sean. To promote it, Posner has created a series of biweekly webisodes documenting his dual life as a college senior and a budding pop star; so far, he's managed to maintain a full course load with a 3.6 GPA, although "there's a lot of homework that gets done on planes," he says.

To date Posner has opened for such acts as Gym Class Heroes, 50 Cent and Akon, but his favorite part of touring is the chance to interact with fans.

"People seem amazed that I'll talk to them, or that I'll listen to their music if they give it to me," he laughs. "But that's just who I am. Basically, if you write on my Facebook wall, I'll write back." At this rate, he'll be making plenty of posts in the coming months.