After the surprise, a gradual welcome

It was billed as a mystery concert. Fans knew where and when: Friday night at House of Blues in Anaheim. But they didn’t know who. They were promised free admission and a major Latin music act.

At showtime, a hostess teases the crowd by inviting it to guess the evening’s mystery performer.

“Skakira!” shouts a wishful thinker.

“Rush!” ventures a wisecracker.

“Frida Kahlo!” says someone expecting a seance.

With no introduction, out comes the band: three crack percussionists on drums, congas, timbales and tambora -- the last a wooden, kettle-like folkloric instrument; a wiry, long-haired wizard on electric guitar; and a staid but skilled woman on electric bass.

Finally, a singer emerges, looking like a cross between a rocker and a Santero: frizzy reddish hair, shiny black pants, necklaces of beads and leather. He’s carrying a small curved horn that appears borrowed from an Alpine yodeler.

The band launches into an unsettling song about an irresponsible louse named “Juancho.” Ripping guitars and thundering percussion disturb the character’s comfort while the singer screams to shake him out of his hammock and wake him from his indifference and intolerance:

“Y tu in-to-ler-an-ciaaaaa !!”

The crowd is unmoved. The singer finally speaks: “We come from Colombia, and it’s an honor to be with you.”

“Who are you?” shouts a voice.

It’s Cabas, unmistakably.

This talented Colombian newcomer seeking to make a name for himself had just flown 13 hours from Buenos Aires to appear at this invitation-only promotional event.

Sponsored by Miller Genuine Draft, the mystery concert series is in its sixth year, having featured major alternative bands (Cafe Tacuba, Aterciopelados, Jaguares) at small venues from New York to L.A.

Guests win invitations mostly through contests. For an artist like Cabas, with his challenging fusion of traditional rhythms and aggressive rock, the show provides a chance for much needed exposure.

It also poses a risk. The crowd Friday didn’t quite know what to make of him at first. Concertgoers’ reserved reception unnerved the band, and Cabas struggled to connect.

But then the singer stepped up to an electric piano and played a soft and lovely intro to his tropical hit “Ana Maria,” a song of overpowering desire.

The fans finally clicked with what makes Cabas so compelling -- rich melodies, smart lyrics, unvarnished emotion and accomplished musicianship. The singer-songwriter, who also plays the flute-like gaita, performed with the same group that appears on his debut EMI Latin album, one of the year’s best. On stage, they displayed an exciting improvisational spirit, part salsa, part blues, part Latin rock.

And they were just the opening act. The headliner, Mexico’s excellent Elefante, did only two numbers because its lead singer had visa problems and never showed. Cabas pitched in on Elefante’s catchy hit “Asi es la Vida” (That’s Life), reading lyrics scribbled on a page.

The young Colombian returned with his band for a rousing encore that left the crowd cheering.

No mystery there anymore.