CIUDAD JUÁREZ, Mexico – With their polka-inspired music and gritty lyrics, norteño groups along the Mexico-Texas frontier have long documented the trials of border life and have turned the north's drug lords into living legends.

Now some of the musicians are apparently in the crosshairs of the rough-hewn men they croon about in narcocorridos, the narrative songs with journalistic-like details of drug shipments, boastful taunts, and bloody revenge.

Late Wednesday, norteño singer Javier Morales Gómez of the group Los Implacables del Norte was slain, gunned down in the plaza of Huetamo in Michoacán state. Three days earlier, singer Lupillo Rivera was shot at while driving his SUV in Guadalajara.

Last month, singer Valentín Elizalde was shot to death in Reynosa – across from McAllen, Texas – after singing a song regarded as sympathetic to the Sinaloa cartel from his home state. The song is called "To My Enemies."

Analysts say the attacks are an alarming indication of how bad things have become in a turf war between the Sinaloa cartel and the Nuevo Laredo-based Gulf cartel.

"It's obvious that for these guys [the narcos], it's not just about making money anymore. They want to do whatever they feel like. And so, if you insult me, if you show a lack of respect in your song, then you die," said Javier Ibarrola, who writes on drug trafficking and the military for Milenio magazine.

The drug fight has become President Felipe Calderón's first item of business since taking office Dec. 1. He sent thousands of army troops and federal police to Michoacán this week in his first attempt at a crackdown.

Analysts say the attacks against musicians also represent another sign that this cartel turf war is different from previous ones, when there were unwritten rules that protected musicians and other "civilians."

The fight today is more like a mafia free-for-all, with no rules or protocol. Captured rivals are typically tortured and sometimes beheaded, and there was a report last week of victims being thrown from an airplane.

One beheading victim this year was a 17-year-old boy, whose killing was later boasted about on an Internet blog where sympathizers of the Sinaloa and Gulf cartel exchanged taunts. And threats were made against Mr. Elizalde, the singer killed in Reynosa, in Internet chat rooms before his death.

A video posted on the You Tube Web site showed images of dead men allegedly belonging to the enforcement arm of the Gulf cartel, the Zetas, set to the tune of the Elizalde song "To My Enemies."

Since the killing of Mr. Elizalde, similar cyber threats have been made against other norteño musicians, like the Tucanes of Tijuana, although it's impossible to tell whether the threats are real.

Likewise, police don't have any suspects in the two recent killings of norteño musicians, or in the attack against Mr. Rivera. Media speculation has taken the place of police work, although the two slayings fit the style of drug hits in Mexico.

"This is the first time I have seen violence in the entertainment industry, I have been doing this for a long time," said Pati Chapoy, who conducts the entertainment television show Ventaneando. "Not only are the gruperos living in crisis, so is the [entire] society." Grupero refers to a broader music genre that includes norteño.

This week, the fear of greater violence caused ranchera music superstar Vicente Fernández to cancel upcoming concerts in Chilpancingo, the capital of Guerrero state near the Pacific Coast, just 60 miles from Acapulco.

Mr. Fernández does not sing narcocorridos, but the state has become a hot spot for violence between the Gulf and Sinaloa cartels seeking control of drug routes and the port of Acapulco. Mr. Fernández was to perform during the city's holiday fair.

According to media reports, other norteño groups have cancelled or may cancel upcoming concerts because of the dangerous climate and death threats.

"I would stay away, too," said Mr. Ibarrola, the magazine columnist. "This is something that is getting very ugly."

Mr. Rivera, the musician who was shot at, said he would not cancel his upcoming concerts.

Mr. Ibarrola said the attacks are ironic in that norteño musicians are known to have performed at parties hosted by reputed drug traffickers, who solicit narcocorridos to enhance their already larger-than-life reputations.

Now, like some journalists before them, the musicians are apparently being drawn into the battle between rival cartels, although Mr. Ibarrola suggests that both groups have had some level of complicity with drug traffickers that puts them in harm's way.

In Ciudad Juárez, across from El Paso, norteño groups rarely suffer from writer's block. There's enough inspirational material, gleamed from the northern border's daily tragedies and triumphs, to fill any playlist.

In bars along the city's main arteries and in the district known as La Mariscal, groups belt out songs with powerful and personal lyrics, about Mexicans dying alone the desert in their effort to reach America, or about a man who returns home to find his loved one in the arms of another.

And then there's the murky, illicit world of drug traffickers. Those storytelling songs carry peculiar risks.

"Sometimes you have smugglers who come up to us and over drinks they tell us about their exploits," explained Raymundo Ramírez, who plays accordion with the band Los Palomos del Norte. "They want their stories made into lyrics, because they have big egos, you know. But sometimes knowing too much information can cost you your life."

Like gangsta rap, narcocorridos are especially popular among young people, but some DJs shun the songs as too dangerous.

Drug violence is rampant in Mexico, with a record 2,000 killings this year, according to figures kept by the Mexico City newspaper El Universal. And entertainers no longer appear to enjoy any protection.

"Sometimes the truth makes people uncomfortable," said Mr. Ramírez. "Sometimes it's better to sing love songs, songs that don't offend anyone."

E-mail liliff@dallasnews.com and acorchado@dallasnews.com

Corrido: a centuries-old ballad style that generally begins with a short personal story followed by a moral. It is the bedrock of traditional Mexican music. It was popular during the 1910 Mexican Revolution to exalt the exploits of Pancho Villa and Emiliano Zapata.

Narcocorrido: a modern version of the traditional ballad that is dedicated to the real or imaginary exploits of drug traffickers, mostly in northern Mexico. The songs are sometimes requested or paid for by the traffickers themselves or based on media reports.

Norteño: a musical style popular along the Mexico-Texas border that is influenced by accordion-dominated polka music. It developed in rural northern Mexico in the early 20th century. At its heart is a corrido, a personal tale followed by a moral.

Grupero: a more general term to describe several forms of Mexican music, such as norteño, tejano, or a mixture of different forms.

Ranchera: Romantic ballads often sung to mariachi music, which includes guitars, violins and horns.