The rally for immigration reform became a singalong Tuesday afternoon for thousands on the otherwise shutdown Mall. Los Tigres del Norte — the biggest, most beloved band that many English-speaking Americans have never heard of — were onstage, and almost everyone in the audience seemed to know every word.

Enraptured participation is typical fan behavior the world over, of course, but the explanation for the phenomenon at a Los Tigres show is a little special. Their lyrics are like news bulletins from the lives of immigrants. Some members of the San Jose-based band — whose name translates as “the Tigers of the North” — were once undocumented immigrants from Mexico.

“We all have experienced some of what they are singing about,” said Emma Flores-Klein, an office worker from Salisbury, Md., who came from El Salvador 28 years ago. “We don’t have it all. We don’t have our families. We make so many dollars, but we can’t share our love with our loved ones.”

Which is basically the message of the Tigres song “The Cage of Gold” — a story of that bittersweet sense of accomplishment in a new land at the cost of losing connections in the old one.

“All their songs express what the people feel, and the majority of their songs are true,” said Ixsa Robles of Arlington, who sang along to the song “Jose Perez Leon,” which, she explained, “is the story of immigrants who wanted to cross to here and asphyxiated on a train.”

The devotion spans generations and crosses borders. “I like that they support us, and whenever we need cheering up, their songs are always there for us,” said Kimberly ­Magaña, 13, Robles’s niece. “My dad is a number-one fan.”

“Los Tigres haven’t forgotten their humility,” said Nelson Medina, 42, visiting from Honduras. “They understand the aspirations of the people.”

Appeal without borders

Los Tigres del Norte — four brothers and a cousin — looked like businessmen in their dark suits at breakfast in a downtown hotel Tuesday. They maintain courtly, old-world manners. As each entered the breakfast area, he walked around the table, shaking hands with associates and kissing fellow band members on the cheek.

They had played shows in three towns in Mexico on Friday, Saturday and Sunday, finishing between 3 and 5 each morning. Shows usually end that late in order to satisfy all fans’ requests for songs and photos. Los Tigres are scheduled to perform and be honored Wednesday at the Billboard Mexican Music Awards in Hollywood. Then they are off to perform in Bogota, Colombia’s capital.

The logistics are staggering. They have a Mexican set of equipment — for shows in that country and internationally — and an American set of equipment. The Mexican gear was pressed into service for Washington, because the American set was needed in Hollywood. Both sets include drums, accordions, electric bass, saxophone and three bajo quintos or bajo sextos, which are 10- and 12-string guitarlike instruments.

Usually the band members come in for breakfast after a show, then sleep until late afternoon. This time, they were due for a sound check on the Mall at 9 a.m.

“We’ll see how our bodies react,” said Jorge Hernandez, the eldest brother and leader of the band. He’s about 60 and sings and plays accordion. “Since we were little kids we have traveled. We don’t have another life.”

Brothers Hernan, Eduardo and Luis Hernandez and cousin Oscar Lara round out the group.

In a car on the way to the Mall, Hernan told the story of how Los Tigres came to be. In 1968, after the brothers — including some who are no longer in the band — had been playing for a few years as children to support the family, they were offered some gigs in California. They had temporary work visas. A border agent asked the name of the band. Since they didn’t have one, and the agent was impressed with their drive, he called them the Little Tigers. They modified it to be the Tigers of the North.

A promoter stole their documentation in California. They overstayed their visas. Now all are citizens, except Eduardo, who is a legal resident.

Early on, they hit on the formula of writing songs about the lives of their audiences. “We noticed how our fans lived and worked,” Hernan said.

One of the first songs in that vein, from the early 1970s, was “Vivan los Mojados” — “Long Live the Wetbacks.”

Their sound is known as norteño, a kind of Mexican country music featuring high, tight harmonies, a strong one-two beat and carefully enunciated words. Their preferred song form is the corrido, a narrative slice of life. They have recorded 500 songs, sold 37 million albums and won six Grammys and six Latin Grammys.

“We have, I think, 30 songs related to immigration, so it’s easy for us to put together” a program for the rally on the Mall, Jorge said. “We don’t do imagination. We do the real stuff.”

‘Mas congresistas!’

The plan at the rally was for Los Tigres to weave together four blocks of songs that would reflect some of the themes that speakers would address between sets of music — including immigrants who die trying to cross the frontier, children whose parents are deported and immigrant soldiers who give their lives for the United States. CASA of Maryland and the Service Employees International Union organized the rally.

“Our lyrics are not fads,” said Luis. “With songs like ‘The Black Door’ ” — about frustrated love — “and ‘Three Times a Wetback’ ” — about crossing from El Salvador to Guatemala to Mexico to the United States — “time goes by and those songs are still in the minds of the people.”

In a tent behind the stage, the band members changed into their black boots, shiny gold pants and tiger-print blazers. Jorge and Hernan paced around singing scales to warm up their voices. Jorge donned a black Stetson cowboy hat with the Los Tigres del Norte label. A parade of nearly a dozen members of Congress came to ask for photos with the band — an excellent trophy for appealing to Latino voters.

The band was about to go onstage when word came: “Mas congresistas!”

More members of Congress.

The introduction of the band by House Minority Leader Nancy Pelosi (D-Calif.) was drowned out by the roar of the crowd, pressing toward the stage with cellphone cameras raised. The first figures Jorge played on his accordion were enough for the audience to recognize “De Paisano a Paisano” (“From Countryman to Countryman”) and the group singing began.

I’ve spent my life exploring other lands

To give my children a better tomorrow.

Next was “Mis Dos Patrias” (“My Two Countries”):

Don’t call me traitor, I love my two countries.

In one I left my dead, here my children were born.

Lila Downs, another star of Mexican American music, came onstage to sing two duets with Jorge, including “The Cage of Gold.”

“Basically they’re like historians, musical historians, who really explain in very simple words the immigrant experience,” Downs said of the band backstage before the performance.

Now she and Jorge conjured the drama of a heartsick, undocumented immigrant. He feels trapped in his home, afraid of deportation, pining for Mexico, needing his American job, while his children forget their Spanish and don’t care about their roots.

Jorge and Downs, and hundreds of supporting voices, join on the chorus:

Even if the cage is made of gold,

It’s still a prison.