MEXICO CITY: In the golden age of mariachi, thousands of music lovers would crowd into theaters and fancy restaurants or fill the Plaza Garibaldi in the heart of the capital just to hear their favorite tunes played on guitar and violin.

On a recent evening in the same plaza, that golden age was a distant memory.

Roving bands of musicians chased down cars on one of the city's busiest avenues, leaning into windows to bargain over the price of a song. Black-clad musicians in cowboy boots then assembled ragtag groups that played out of tune while singers hoarsely belted out mournful ballads about love and heartbreak.

The aching music may remain one of Mexico's top cultural exports, by which the country is known worldwide, but its fortunes have fallen in its homeland, with few well-trained musicians and few decent venues to play in.

A new mariachi school in Mexico City is seeking to revive a music that's lost ground over the years and that sometimes seems relegated to commercial jingles and elevator Muzak. Called the Mariachi School Ollin Yoliztli, meaning life and movement in indigenous Nahautl, the school teaches folk bands how to play professionally while grooming a new generation of songwriters and composers.

''What this school will do is dignify mariachi music,'' said director Leticia Soto.

Housed in a former nightclub on the plaza, it's Mexico's first professional school dedicated to the genre. Eventually, Soto said, she hopes to offer Mexico's first university-level degree in the music.

Another school in the western state of Jalisco, the birthplace of mariachi, offers workshops but not a degree.

The goal is to formalize a music that has largely been passed down among the generations, without formal instruction.

Last year, UNESCO recognized mariachi as an Intangible Cultural Heritage of Humanity, and the city has tried to protect that heritage by both cleaning up the plaza and helping set up the school.

Most of the more than 2,000 musicians who ply their trade at the newly renovated colonial plaza learned to play traditional favorites such as ''Cielito Lindo'' and ''Guadalajara'' from their parents or other relatives. Most of the players there can't read music and run through the songs by ear.

Miguel Martinez remembers a different time. The 91-year-old began playing the trumpet 78 years ago in the Plaza Garibaldi, when there were only five mariachi groups working there, with only two including trumpet.

He joined the Mariachi Vargas de Tecalitlan, Mexico's top ensemble, in 1940, when the music was featured almost daily on the radio. Hundreds also packed the Blanquita Theater for shows that included some of the top singers of ranchera, another, more guitar-based genre.

''It makes me very sad to see what these mariachis have done to the music that el Mariachi Vargas did so much to honor,'' Martinez said.

''The truth is that I would leave this world very happy if I could see that our folklore will continue, because we were losing it.''

With that in mind, he called the school ''a fantastic idea and something that authorities should have done a long time ago.''

For guitarist Arlette Gudino, one of a dozen women accepted at Ollin Yoliztli, playing mariachi music is a passion passed down by her trumpet-playing great-grandfather.

''There are places outside of Mexico where people get more excited to listen to mariachi than here,'' said the 23-year-old actress.

''I would like to do something to get people to value the musical treasure we have.''

The 102 members of the first class range from a 14-year-old junior high school student to a 68-year-old retired nurse. They started school last week and are scheduled to graduate in three years with a technical degree.

During that time, they'll learn music theory and mariachi history and be taught how to sing as well as play the trumpet, guitar, violin and the round-backed guitar called the vihuela.

Trumpet player Raul Rosas, 38, who waits in the plaza for clients, admitted he and the other musicians there could use some training.

''We all should go that school because we don't play the music like it should be played,'' said Rosas, one of nine brothers who play in mariachi bands. ''We're musicians who play by ear, why fool ourselves?''

The first mariachi bands, in the 18th century, played only stringed instruments and dressed in white cotton fabric, huarache sandals and wide-brimmed straw hats, the clothing of Mexican farm workers of the time.

Trumpets were added in the early 20th century, and mariachi bands began wearing the more elegant charro, or cowboy, outfits familiar to modern audiences: a short, embroidered jacket, snug-fitting pants with shiny buttons along the legs, fluffy bow ties and the iconic wide-brimmed sombreros.

By the mid-20th century, mariachi music had become a widely popular symbol of Mexican culture, played by radio stations and featured in charro films during the country's Golden Age of cinema, from 1935 to 1959.