Smule, the maker of the popular iPhone apps, such as the Ocarina, Glee Karaoke, Magic Piano and I Am T-Pain, raised $12 million in new funding, from returning invetors Shasta Ventures, Bessemer and Granite Ventures.

The fresh capital brings the company's total amount raised to $25.5 million, since launching in 2008.

Smule, which started charging a minimum of $1 for its apps since inception, has grown its advertising-paid model quite a bit. With 17 million users (about half of which are in North America), Smule is on its way to cross eight figures for its trailing twelve months in revenue, said Jeff Smith, founder and CEO, in an email to me. About a quarter of sales come from advertising, Jeff added.  

 Smith, who founded email security software company Tumbleweed, and led it through an IPO until he stepped down in 2005, founded Smule with Dr. Ge Wang, an Assistant Professor at Stanford University, at the Center for Computer Research in Music and Acoustics. 

We've been following Smule since it launched back in 2008. Check out an early interview with Jeff, in which he plays the just-launched Ocarina. Here's our mini-documentary on Smule.