With the phenomenal success of rootsy bands like Mumford & Sons, bluegrass has never been hotter -- and it looks like some of that heat has spilled over to the Bakersfield festival devoted to the music.

In the six years since its inception, The Great 48 Hour Bluegrass Jam has landed a number of respected performers but none as big as Rhonda Vincent, who headlines the show with a concert at the DoubleTree Hotel on Friday.

"Rhonda is the queen of bluegrass and Josh Williams is the best flat picker there is," said festival organizer Kelvin Gregory. "That adds a whole new dimension to Rhonda's show. Whenever you get big-time hitters like those two interested in playing, you gotta go for it."

The four-day festival -- a mix of live performances, workshops and nonstop jamming through the halls of the hotel -- is sponsored by the California Bluegrass Association, and most of the events are free, with the exception of tonight's opening festivities and the Vincent concert.

"If someone has never been exposed to bluegrass, they owe it to themselves to come out and see what the buzz is all about," said Gregory, who counted 500 attendees over the course of last year's festival, though he expects to exceed that figure this weekend.

"I'd say the interest in bluegrass is bigger now than it has been in the past."

Kicking off will be the energetic Showcase Showdown concert fundraiser, featuring groups The Get Down Boys, Grasslands, Red Dog Ash and Grassfire. Proceeds from the concert benefit the Leukemia & Lymphoma Society of Kern County.

The main event comes Friday night, with Vincent's appearance in one of the hotel's ballrooms.

Among the best-selling bluegrass artists of all-time, Vincent is also one of the most heralded and comes from a family of bluegrass performers stretching back five generations. She started her career as a child in her family's band, The Sally Mountain Show.

"When I started singing at 3, then joined the group at age 5, we had a TV and radio show and made recordings," said Vincent during a recent phone interview. "It was more a way of life before it was a career. My dad would pick me up from school every day, and my dad, grandpa and I would play until dinner. Then friends would come over and we'd play until bedtime. This was an everyday occurrence. We would travel all over the world and perform. It was wonderful on-the-job training. My mom used to say she took us off the bottle and put us on bluegrass."

Vincent has built an empire under her own record label, Upper Management, releasing her own CDs and embracing the Internet as a way to find bluegrass aficionados.

"One of the things we did when we started a website was put our tour dates up. That was such an incredible tool. Now you can go on iTunes and check out our music. Things are no longer dictated by what's on a radio station and their playlist."

Vincent's latest release, "Sunday Mornin' Singin'," her first all-gospel recording, has been years in the making. The singer said the project literally took her back to her hometown church in Greentop, Mo., which has remained frozen in time.

"We showed up with a film and studio crew, but the church still only had two power outlets."

Beyond some electrical ingenuity and recording equipment powered by her tour bus parked outside the church, Vincent said the project was blessed with some divine intervention. Upon its release, the album has become the highest-selling release of her career.

"I didn't expect it to be released commercially. If radio chooses not to play you, you can go online and listen for yourself. Bluegrass is a music that has benefitted from that. Normally, a lot of listeners may not think they like bluegrass, but then when they hear it, they like it."

Vincent recalled one of her early visits to Bakersfield when she was beckoned by Buck Owens to give a solo performance in his office, a regular request made to artists visiting the KUZZ radio station.

"Back in the '90s, we did this radio tour and we stopped by. I met Buck Owens, which was one of the most nerve-racking experiences I've had. It was just Buck and I in his office. I had my mandolin. He says, 'Sing me a song.' From that, he called Nashville a little while after I got home and asked, 'I wanna know what kind of mandolin that is. I want one just like it.' And he bought one exactly like mine. Several years later when I put my first bluegrass band together, Buck Owens was in the front row of our show in Bakersfield. That was pretty cool."

Joining her band, the Rage, will be longtime flatpick guitarist Josh Williams, who makes a return to the group after a four-year absence.

Following Vincent's concert, the music continues with an addition to the schedule of free performances with the Music Caravan Mid-Night Showcase at midnight on Friday and Saturday and featuring groups The Drifter Sisters, Hello Trouble, The Roustabouts and The Central Valley Boys.

In addition, there will be a number of daytime workshops and the ever-popular open mic and band scramble, in which participating musicians will throw their name into a bucket associated with their instrument before being paired up with another musician to perform together onstage later that evening. All ages are allowed and family participation is strongly encouraged.

"I'd love to invite the community out to see what we're doing out here," said Gregory.