Though the title of Colbie Caillat’s sophomore album, “Breakthrough,” has nothing to do with how her career took off, the word literally defines her path to fame.

Raised in L.A., the self-described beach girl and “lazy teenager,” whose performance caps a free, nine-band concert at Baylor University’s Diadeloso 2010 on April 22, started writing and recording songs just for fun. A friend told her about Myspace and made her a page so she could post her tunes, and six months later, she was Myspace’s number one unsigned artist, getting 50,000 plays a day.

Labels came calling. Her first single, “Bubbly,” became so huge, it carried her maiden album, 2007’s “Coco,” to a top five debut on “Billboard” magazine’s Top 200 album chart.

Sure, Myspace sensations are common these days, but when one considers how many would-be stars are now seeking that route to renown, breaking through is still an impressive feat—especially when you’re not even trying.

“It was just, like, a hobby,” Caillat confessed during an interview that takes place in quintessential California mode: while she’s driving. Though she recorded with a real producer, Mikal Blue, who was a friend of her father’s, she never scheduled or paid for studio time; never advertised or campaigned for adds to fans’ Myspace pages. The ultimate irony, though, is that, as the beautiful, talented daughter of rock royalty—her father, Ken Caillat, co-produced one of the biggest-selling albums of all time, Fleetwood Mac’s “Rumours”—she might have been able to hook herself up with a record deal anytime she wanted. She just never needed to.

More than 2 million discs and 6 million single downloads later, the pressure was on to prove that success wasn’t a fluke. But Caillat’s sunny voice, matter-of-fact subject matter and ability to co-write easily with hitmakers—and a little help from Dad, who co-produced—helped turn “Breakthrough” into another winner. “Fallin’ For You” is already a hit, propelled by a super-cute video co-starring “Saturday Night Live’s” Bobby Moynihan as a clumsy, opposite-of-hot guy whose goofy humor and bumbling attempts to woo her are so adorable, he wins the willowy blonde over in the end.

Singer Colbie Caillat performs at the BMI 57th Annual Pop Awards in Beverly Hills, Calif., on May 19.
Associated Press, file

That video, and her naturalness in it, belies another irony about Caillat: Until recently, performing live terrified her.

“When I was young, I wasn’t completely chubby, but I was definitely, like, thicker,” she revealed. “It made me shy. Like, being uncomfortable in my own skin, and that really just stayed with me all through high school, through everything.”

She admitted she got so scared before live performances, she would literally cry. “Breakthrough” is about getting over that fear.

“I had this little breakdown where I was so stressed about the work that was to come for this new record, and I didn’t know if I was ready to handle it,” Caillat said. “I just remember telling myself, I can’t feel sorry for myself anymore. I just turned 24. Get over it. Everyone has fears and insecurities in life, and you just have to work on things every day to break through them.

“And so I would challenge myself,” she said. “I learned how to have fun with things and not take myself too seriously.