At the opening night of the 53rd Monterey Jazz Festival, French/Chad world music sisters Helene and Celia Faussart had the main stage audience enraptured with their cool soul grooves and colorful garb and make-up. Roy Hargrove's Big Band and guest singer Roberta Gambarini had the packed Dizzy's Den venue jumping to Bob James' "Nautilus" and swooning to Cole Porter's "Every Time We Say Goodbye," which was perfect accompaniment to a grassy lawn dotted with lounging couples and relaxed friends talking in circles.

But San Francisco's Jazz Mafia has a killer concept: a 45-person big band jazz orchestra, fronted by trombonist and conductor Adam Theis, that crosses over into hip-hop, soul, classical and funk territory.

At the Jazz Festival's Dizzy's Den venue Friday night they played a set that lead with their 1-hour suite called "Brass, Bows and Beats" that merged and mixed those genres, then did a variety of encores like Astor Piazzolla's "Fugata," their own chronological music-history hip-hop suite "Take it Back," and a slow jam called "Love Song."

It was an eclectic show. At times it recalled Duke Ellington, complete with mighty blasts of brass, but they would drop a Snoop Dogg "sample"; they deployed a beatboxer and stretches of a cappella singing and rapping, with the string, brass and horns playing snippets of melody like a DJ would employ breakbeats, but with Theis (in an untucked dress shirt, jeans and wallet chain dangling) conducting the affair like a hipster Cab Calloway, and solos flaring out of the wall of sound to display musical chops.

It was a performance that started with a foundation in big band jazz, but, like the M.O. of the Jazz Fest, reaches out, inclusively, to a variety of music. Last year folk icon Pete Seeger, gospel-infused blues of John Scofield and the Piety Street Band, and world music spinner DJ Logic were invited in; this year the variety is repped by eclectic classical music maestros Kronos Quartet, the Latin flavored Septeto Nacional de Cuba, and Jazz Mafia, whose founder found time to talk after their set.

"[As a kid] I was into skateboarding, punk and ska," he said. "I never listened to much classical music. When I heard big orchestra jazz, the sheer size and might, but tamed, I thought that was cool."

He cited jazz composers and bandleaders Gil Evans and Oliver Nelson among his influences, but revisted the classical music equation by citing "Impressionistic 20th Century" composers Igor Stravinsky and Maurice Ravel, too. Apparently, he threw all his musical influences in the pot to concoct Jazz Mafia 13 years ago, the success of which can be measured in its longevity, multiple spin-off projects, sold out gigs at San Francisco's Palace of Fine Arts and Yoshi's, and the standing ovation they received by the Monterey Jazz Festival audience Friday night.

About that audience, Theis said, "It was a sit-down audience. The crowd wasn't as high-energy, but they were attentive, responsive at all the right places. It was one of the best audiences."

High-energy crowds, he said, just want loud.

"A hip-hop crowd is going to be skeptical. 'Okay, let's see where you're going with this.'" A jazz crowd, he said, can be equally discerning.

"It's hard to do the cross-over," he said. "You have to make it entertaining, we had to have a melody, but you can experiment."

Though Theis is the leader of this youthful collective, during the set he gave shine to soloists and singers, taking his place in the back of the orchestra and picking up a trombone to accompany.

"There has to be strong leadership, but we're pretty democratic. The next symphony is a 10-person collaboration."

Later, in another sign of their proximity to youth culture, one of the MCs, Seneca, was walking and hawking his solo CDs, hand to hand. Now that's hip-hop. And that's sign of an expansive reach the Jazz Festival weilds, in addition to the world-class jazz musicians who will line this weekend.