It’s not so much what they do, it’s how they do it. That’s the mantra for a Los Lobos concert.

For their second appearance at the Robert Mondavi Winery this decade, the musical wolves of East L.A. set a sell-out crowd (the first of the 2007 season) on fire Saturday night with a mix of musical styles that virtually define this melting pot of a nation.

It was musical nirvana. Honestly, who could help but marvel that Grammy Award-winning Los Lobos has been making such great music together for four decades now?

Listening Saturday night to the exceptional sextet wrap up this year's Robert Mondavi Summer Music Festival, one had to truly marvel at how this group of talented musicians was able to turn a passion for rock ’n’ roll and its Mexican-American roots into a winning combination embraced by middle America.

No doubt, these guys have music instead of blood running through their veins. And it’s a well known fact that a good portion of the combo's enthusiasm — especially in live concert — comes in the give-and-take with the group’s die-hard fans.

Considering that they scrapped most of their post-intermission set list for a foray into widely divergent rock classics, Saturday night’s gig made that point in spades.

I doubt the four schoolboy friends envisioned what was in store when they first came together in 1973 to perform popular songs of the day by the Rolling Stones and the Beatles.

David Hidalgo, Cesar Rosas, Louie Perez and Conrad Lozano met as students at Garfield High School in East Los Angeles. Lozano had been a member of Tierra, the most popular Latino band of the day. Influenced by the era’s political and cultural stirrings, the four young musicians started looking into the traditional Mexican music their parents played at home. It didn’t take long for them to put together their own distinct Tex-Mex style.

Yet the repertoire is much more than what comes to mind when the label “Tex-Mex” is applied. During the generous two-hour-plus performance at the Mondavi winery Saturday night, fans heard not only traditional Mexican influences, but fiery salsa, Colombian cumbia as well as mambo, bolero and bachata. It goes without saying the underlying theme is good, old-fashioned, kick-ass rock ’n’ roll.

It’s plain, too, that Los Lobos is about musical family as well as music, reflected in the fact that the Los Lobos of 2007 is the same four guys who started the band four decades ago, with the addition of reedman/keyboardist Steve Berlin, who joined in 1983, and, more recently, drummer Cougar Estrada.

Whether serving up a simple two-step backbeat or building layers of guitar and keyboard sounds on top of thundering percussion, whether playing electric guitars or acoustic instruments employed by their Mexican precursors — guitarron, button accordion — Los Lobos pleases its audiences with a varied mix of very danceable rock as well as very danceable Latin musica.

The evening’s varied program included traditional ranchero (“La Pistola y El Corazon”) with Hidalgo’s rousing accordion, an old hip-snaking mambo (“Porro”) as well as a bachata from the “Kiko” CD, “Arizona Skies,” sung en español by Perez. The wildly successful “Kiko” was represented as well by the earnest narrative, “When the Circus Comes.”

But it was the dance material this crowd had come to hear. The most eager audience members got a taste before the break with one of the best numbers, “Chuco’s Cumbia,” from the latest recording, “The Town and the City.” It was a rhythm we’d get a lot more of during the extended second half.

That began with “Valley,” another number from the newest CD, one with a decided rock bent.

It appears that inspired Hidalgo to deviate from the set program, to sing and play an R&B tribute to Fats Domino. The brief foray into R&B, in turn, prompted a nostalgic leap back to 1984’s “How Will the Wolf Survive?” with the straight-ahead rocker, “I Got Loaded,” bringing the dancers to their feet.

More nostalgia followed, with Hidalgo breaking into Ritchie Valens’ beloved “Come On,  Let’s Go,” trailed by The Temptations’ “Papa Was a Rollin’ Stone,” and even an unexpected inquiry into our well-being with Carlos Santana’s “Oye Como Va.”

More danceable cumbia was next on the bill, as was the treasured norteño ballad, “Volver, Volver.” Encores ranged from blues to another rock classic, Neil Young’s “Cinnamon Girl.” It seemed as if nothing was off limits — Los Lobos could do it all. And did.

“We make music because that’s what we were put on earth to do,” says Perez. “It’s what we’re good at.”

Can I get an “Amen?”