But alas, it's not Mama Haim who's helping them sell out venues all over the world. These ladies managed to drum-up interest in their band all on their own the good ol' fashioned way: opening up for over 20 different bands including Mumford and Sons, Florence + the Machine and Rihanna.

Though their rigorous touring schedule caused them to delay the release of their debut, Days Are Gone�which is finally coming out on September 24�it ended up earning them a fan in Jay Z, who added them to the Roc Nation roster.

Ask the Haim sisters how they got the news about being signed to Hov's label and they'll joke that they got a call on their magical bedazzled Jay Z phone. "The ringtone is 'Brush Your Shoulders Off,'" Alana said. In reality their manager was signed to Roc Nation and they followed him over. But the man they just call Jay was more than happy to have them.

"We honestly didn't expect him to even know the first syllable of our band name," Alana said about the first time she met her boss. "But he was just so nice. He just said like, 'You guys just know what you're doing. We're just really excited that you want to be a part of the company.'"

Jay's right, these three Californian sisters definitely know what they're doing. Mainly because they've been doing it for most of their lives.

The girls first started playing the local festival circuit in elementary school as part of their family band with their mom and dad, Rockinhaim. Their parents taught them classic rock covers like Van Morrison's "Brown Eyed Girl," which featured Danielle on guitar, Este on bass and their baby sis, Alana�who was only four years old at the time�on maracas. "Our parents couldn't have picked a more difficult song for us to learn as our first song," Este said.

But Alana defended their choice: "It's kind of like how you learn how to swim. You just gotta jump in there."

Soon the sisters�who call Karen Carpenter and Chaka Khan two of their biggest influences�were writing their own songs as a three-piece and playing local clubs. Not every show back then was perfect, but they learned something new every time they hit the stage. "I think every band starts out that way, playing local shows to small crowds," Danielle said. "You play until someone listens and hope for the best."

Now a lot of those someones are anxiously waiting to hear their upcoming debut, which is a tightly produced version of their percussion-heavy live show that the girls spent the last year working on. Tour dates made it hard to hit the studio, but the sisters admit that their perfectionist tendencies also slowed things down quite a bit.