SUCRE, Bolivia » The band members wore black. The lead singer screamed into his microphone and whipped his long, black hair around. The guitarists clawed at their instruments. The drummer pounded with fury. And then the panpipe player took his solo, and the fans packed into the mosh pit went into a frenzy.

This is heavy metal, Bolivian style, a clashing fusion of thrashing guitars and shrieking lyrics with the rhythms and instruments of Andean folk tunes, its roots, not just pre-Columbian, but pre-Incan.

"It’s social syncretism, the fusion of two cultures," said Veronica Huanca, 26, a lawyer who bounced enthusiastically during a concert here last month.

At one point, she and her friends formed a ring and danced in a circle, arms on one another’s shoulders, a mosh-pit wink at a traditional village dance. "It’s like the baby Jesus in a poncho and chulo," she said, using an indigenous word for the colorful wool cap with ear flaps often worn in the Andes.

Bolivia is the poorest country in South America, with a high percentage of indigenous people, many of whom live lives locked in tradition. But it is also a thriving, fast-changing, youthful country where old and new, foreign and homegrown, meet, clash and mix.

Here in Sucre, the black T-shirts and tight black pants of the metaleros, as heavy metal fans are known, stood out against the whitewashed walls of the colonial buildings.

The first band to take the stage at what was billed as Metal Fest Sucre was Armadura, a group that has helped pioneer what it calls heavy metal fusion. The concert was part of a tour to promote a CD in which several bands played a heavy metal version of songs by an iconic Bolivian folk band, Kalamarka. The album, with songs with very unmetalesque names like "Clear Waters," "Mommy" and "When the Potato Plant Flowers," is called "Metal Marka."

Only a handful of groups have embraced the hybrid style, and even Armadura, whose name means armor, plays just a few such songs in sets dominated by unadulterated heavy metal.

Still, those songs, characterized by the use of the panpipe, known as the zampoqa, and a wooden flute called a quena, have a special impact among fans.

"They react much better to the songs that are combined with wind instruments than what you see with a lot of songs that are pure metal," said Boris Mindez, the lead singer of Armadura, who wore black leather pants and a black shirt.

The folk songs on Armadura’s set list include one whose title and refrain contain what many regard as the Inca moral code. As the band’s traditional instrumentalist, Yuri Callisaya, shrilled on the quena, the band’s fans sang along with Mindez: "Ama sua, ama llulla, ama quella," which translates as, "Don’t steal, don’t lie, don’t be lazy."

Armadura’s fans include the U.S. Embassy in La Paz. The group played at the embassy’s Thanksgiving party this year, and the Metal Marka concert tour was partly financed by the embassy.

Both Mindez, 33, and Callisaya, 34, live in El Alto, a city near La Paz whose population has soared with immigrants from the countryside.

The fast-growing city is critical to understanding the changes swirling through Bolivian society, a crucible where old and new mix and where young people experiment with Western musical genres, but hold on to their musical roots.

"This generation of young people, 14, 15, 18 years old, they were born in El Alto, but their parents are immigrants, so they play hip-hop, they play rock, they play reggaeton. They have a whole world of genres, but their families keep the traditions, such as making the payment to the earth in August," Callisaya said, referring to a traditional agrarian fertility ritual.

Heavy metal would seem an unlikely match for the usually soothing sounds of Andean folk music. Yet some metaleros said that their music’s signature aggressiveness had a natural counterpart in a traditional Andean dance and music called tinku.

In small villages like Macha, in central Bolivia, the tinku dancers square off in bloody fistfights, a ritual that is meant to feed the earth with spilled blood and ensure an ample harvest or good fortune for a community.

"A tinku in Macha is much heavier than any mosh pit anywhere in the world," Callisaya said.

A startling version of the tinku was seen in La Paz this month at an event organized by the government to promote the Dakar Rally, a motor-sports race that passes through Bolivia.

While President Evo Morales, diplomats and Cabinet ministers watched, a heavy metal band called Alcoholika La Christo (a name that combines the words for alcoholic and a feminine Christ) blasted out its version of a traditional tinku song, accompanied by a band of panpipe players, while folk dancers whirled through the tinku steps. The metaleros were all in black, the panpipe players wore colorful ponchos, and the dancers twirled under colorful, feathered headdresses.

Alcoholika’s leader, Viko Paredes, 35, was perhaps the first to mix the genres. Living in Washington in the late 1990s, he frequented a Bolivian restaurant across the street from a nightclub that played techno dance music. Music from the two places would mix in the street, and it gave him the idea to meld his favorite music, heavy metal, with the Andean music of his homeland.

"What I try to do is show Andean music with the power of rock," Paredes said.

As he experimented, he brought in Fernando Jiminez, one of Bolivia’s foremost zampoqa players, as a collaborator.

Jiminez, 50, said that combining the musical styles was a challenge.

"Folk music is more about conviviality, fiesta," Jiminez said, taking a break from recording an album of traditional songs in La Paz. "It’s not aggressive. It has been a cultural clash."

At the concert in Sucre, which included bands with names, in English, like Nordic Wolf and Murder Machine, there were some among the several hundred who attended who felt that there was more confusion than fusion on display.

"Everything has its place," said Roger Rosales, 36, who goes by the name Pazuzu and leads a band called Bael, which he described as a black metal band. A burly man with a shaved head and a pentagram tattoo on his right arm, Rosales said he was a Satanist. He was also a purist. "Metaleros should stick to metal, and folkies to folk," he said.

But for Mindez, of Armadura, the proof of the hybrid’s success is in its fans.

At some concerts, the dancers in the mosh pit hold hands and break into steps whose origins go back centuries.

"They push each other around, but lots of times when we’re playing with wind instruments, the people start a fusion between the dance of the altiplano and rock," Mindez said, referring to the Andean plateau. "It’s a total mix."

© 2014 The New York Times Company