There's no harm in calling "Cruzar la Cara de la Luna" a mariachi opera. Houston Grand Opera has to attach some kind of description to it, if only to give potential ticket buyers an idea what it is.

But let's put that label in perspective. "Cruzar" has more mariachi in it than opera, and that's all for the good. Its appeal lies mainly in what makes it different from most opera.

Above all, there's the mariachi music by Jose "Pepe" Martinez. Not only is it suave and melodious, but its almost unceasing glow reaches into the souls of the characters: No matter what disruptions and hardships they face, they hold onto their hopes and forge ahead. They express themselves in simple, heartfelt numbers that come across like songs, not arias. That suits them.

That leads us to another difference from opera. "Cruzar" - the story of a family divided across the U.S.-Mexico border - doesn't engage in the histrionics that opera typically revels in. Even when a central character dies in a desert, no one stops to lament. Life goes on.

If you had to link it to the opera world, "Cruzar" - in English, "To Cross the Face of the Moon" - would be a chamber opera. It has only a handful of characters. HGO's staging doesn't even use a set as such. There's just a bench and a bed, with lighting on a backdrop helping set the mood.

Admittedly, having a mariachi band - Mariachi Vargas de Tecalitlan - stretched across the rear of the stage adds a flashiness that most chamber operas don't have. But when the lights on the band go down, all the attention goes to Laurentino, a Mexican-American nearing the end of his life, and his family.

So HGO isn't doing "Cruzar" any favors by performing it in the Brown Theater, the big hall at the Wortham Theater Center. The story's impact comes from the fact that its characters could be real people. But the Brown Theater dwarfs them. They aren't the larger-than-life figures who typically populate the opera stage.

Even more detrimental: Presumably because of the theater's size, the cast and Mariachi Vargas were miked Thursday at the opening-night performance. The amplification served them badly. The singers' voices often sounded outsize and hard. Mariachi Vargas' violins came across as wiry.

"Cruzar" would probably have been much better served if HGO had staged it in Wortham's smaller auditorium, the Cullen Theater. The audience would've had more of an up-close-and-personal view of the action. There would've been little or no need for microphones.

Be that as it may, the singers - all of whom performed in the work's premiere in 2010 - were completely at home with the music and story.

Brian Shircliffe, playing the American-born son of patriarch Laurentino, set the tone for the lyricism that ran through all of "Cruzar": In the little song about a butterfly that opens the piece, he sang warmly and cozily, accompanying himself on a guitar.

The rest of the cast brought their roles a spirit and sincerity that came across despite any side effects from the microphones. Even the singers whose training was in opera sounded at home.

Octavio Moreno gave Laurentino dignity. Cecilia Duarte captured the flirtatiousness and strength of Laurentino's first wife, Renata. Vanessa Cerda-Alonzo, a mariachi singer, had earthiness and soul as Renata's friend Lupita. Playing Laurentino's Mexican-born son, David Guzman sang with ringing tones that helped "Cruzar" reach its climax.

It built to that climax steadily. Martinez and librettist Leonard Foglia - who was also the stage director - had crafted a concise, fast-moving story. Maybe there were a few times it swept along almost too quickly. Powerful events came and went with little time for their import to sink in.

But there was a virtue in that. When the moment the story was aiming toward finally arrived, and the music did briefly fall silent, the power was that much greater. Was "Cruzar" an opera? That didn't matter at all.