AUSTIN, TX -- In an airy rehearsal hall, Antonio Briseño, a retired music professor with 35 years' experience in classical and mariachi music, guides 65 high school students through the vocal intricacies of "México Trovador," a complicated piece of swooping hills and valleys that many have heard before sung at a boda (wedding) or cumple (birthday).
"You sing with pride," Briseño lightheartedly implores his students. He explains these songs chronicle the trials and triumphs of the Mexican people with a passion so fervent, just the first few strains of a song elicit gritos (yells).
The students giggle. Most are Latino, but it's safe to say not all know Spanish, a likelihood not lost on Briseño, who translates some of the lyrics to impress their meaning.
No, this is not your typical soccer or computer summer camp. Now in its third year, this four-day Mariachi Camp recently held at the University of Texas at Austin aims to immerse young U.S. Latinos into the rich heritage of the beloved Mexican musical genre.
During a quiet break later, Briseño, a fourth-generation Mexican American, muses that mariachi is the music of the people. "The heart of Mexico," he tells NBC News.
"It's so emotional, so close to the heart," he adds, pressing his fist to his chest. "That's why people yell. They yell because they feel it."
Heart and soul. Corazon y alma. The words are uttered frequently at mariachi camp.
Mariachi 'Con Ganas'
"You're playing from your soul and you're talking to the audience's soul, and that's what makes mariachi powerful," Castro tells NBC.
Castro got his start in music at the age of 9, and he has played everything from Beethoven and Bach to the emotionally saturated Mexican rancheras that are the staples of mariachi. In the unspoken compact between audience and musicians, he says, mariachi fans expect more than just playing with precision.
Castro recalls how earlier in the day in another rehearsal space, Jose Torres, a youthful looking musician with a doctorate in teaching at the University of North Texas, imparted a lesson about being unafraid to take liberties with the music.
"We have to have vibrato here because without it we're going to sound like big band. We're mariachi," Torres told the young trumpeters, referring to the pulsating sound musicians give to the notes for effect.
"So audiences don't just want to hear "El Rey," Castro continues. "They want to hear "El Rey" con ganas. Con emoción! (With heart. With emotion!) Every song has its own emotion and that's what needs to be created at that particular moment … I tell my students, 'Don't worry about the notes. Just play them. That's when the music comes alive.'"
The mariachi camp was Castro's brainchild, conceived not merely as a way to sharpen young musicians' skills but to build their appreciation for the history of mariachi. Perhaps most of all, Castro saw the camp as a means to shore up their confidence and to develop future leaders.
"That's what I want," Castro says. "I see all these students as potential leaders in their communities."
With more high schools and universities adding mariachi programs and with the nation's Latino demographic booming, Castro and Briseño are encouraged about mariachi's future.
There are more than 100 mariachi programs in Texas schools, according to the Mexican American School Board Association. Other summer mariachi camps are held by the University of North Texas in Denton. and Texas Tech University in Lubbock.
The legislative body of the University Interscholastic League, which oversees competitions in music, academics and athletics for schools statewide, agreed last year to create a pilot state mariachi competition. That is scheduled for next year.
Mariachi's future would appear to be secure in the hands of youngsters like Marla Gutierrez. a trumpeter and vocalist and a junior at Zapata High School in deepest South Texas, near the Mexican border. The granddaughter of Mexican immigrants, Gutierrez says mariachi connects her to culture.
"I feel like I owe it to them to know where I come from," she says.
"Mariachi is a passion that's indescribable," Gutierrez continues. "You make a connection with the song and automatically you feel you're unstoppable. You're on a fiery journey to somewhere you never thought you could go."
And then Gutierrez says that word again. "And if it doesn't come from your heart," she says, "you're not going to have fun."
During the mariachi summer camp, the students only saw the sheet music for "México Trovador" the morning before they first attempted it. Teaching and learning music is about practice and repetition and the morning session soon settles into the pattern.
For some students, their forte may not be singing; their comfort zones lie in their ability to play their chosen instruments: the trumpet, the vihuela, guitarrón or harp. But in today's mariachi ensembles, most players usually take a turn at the vocals, too. "Hiding" behind the instrument is not an option.
A masterful singer himself, Briseño is a coiled force of energy, coaxing and leading the students with humor, encouragement and demonstration. Almost theatrical, he is perpetually in motion, whirling, swaying, tilting, sweeping the air with his arms.
Then, just before lunch, a run-through produces resplendent results of rich, layered harmonies, lilting high notes and stout lower ones. The campers belt out a full-throated, powerhouse crescendo that would send chills up the spines of the dead.
The room is crackling with confidence now.
"And that's how it goes," Briseño exclaims.