On Saturday afternoon, with their country still enveloped in a seismic political shift, three nationally celebrated Brazilian singers will be in Central Park to perform during the first day of the weeklong Brasil Summerfest.

Two of them, Marcelo D2 and Emicida, are rappers whose music confronts overtly political topics, such as racism, corruption and police brutality, and aligns thematically with Brazil's recent antigovernment protests. The third, Gaby Amarantos, sings a raucous style of party music called tecnobrega, a marriage of corny romantic and electronic fare that few would call political. But Ms. Amarantos, whose outrageous, sexy costumes and effervescence lend her the air of a Brazilian Carnival dancer, is known to rally her legion of fans over women's rights and rainforest protection in her northern Amazonian capital of Belém.

In separate interviews, Marcelo, who is from Rio de Janeiro, and Ms. Amarantos said they participated in the recent demonstrations in their respective cities, while Emicida was traveling on tour but supported them. "My position, as always as a well-known person, is to support the causes of the people," Ms. Amarantos said.

The three singers are in town to headline the third annual edition of the Brasil Summerfest, a citywide series running through July 28 that will also include the world-renowned singer-songwriter Seu Jorge, as well as a handful of others playing an array of styles including hip-hop, samba, bossa nova, forro, jazz and indie rock.

The three performers also have this in common: They grew up poor and remain spiritually tied to their respective neighborhoods. Somewhat paradoxically, this gives them a broader appeal, and not just in Brazil.

"Even though they're from poor neighborhoods, they have this global antenna, an idea that they connect not only with the peripheries of Brazil, but also globally," said Ronaldo Lemos, a Rio-based law professor who wrote a book on tecnobrega. "It has to do with being poor but having access to technology."

The combination allows the artists to draw support from a vast Brazilian underclass that persists even after years of steady, if now faltering, economic growth. Ms. Amarantos, who is 34, still lives in the home where she grew up and performs in her Jurunas neighborhood of Belém, a city that each year hosts thousands of rowdy street parties with DJs, singers, pulsating lights and tall stacks of blasting speakers.

Marcelo, 40, who will reunite on Saturday with the 1990s band that made him famous, Planet Hemp, said he has stayed close to his roots in the two Rio favelas, or shantytowns, where he grew up. "I still play in the favelas, I love doing that," he said. "I talk about that in my music—the care, the responsibilities to your friends and community."

In his own music, 27-year old Emicida sings about the Cachoeira favela on São Paulo's outskirts where he grew up and where his mother and sister still live.

In their early days, hip-hop and tecnobrega were rejected by the cultural elite in Brazil, where the gap separating rich and poor is vast. But as a testament to how that has changed, Ms. Amarantos, Marcelo and Emicida are all able to fill large stadiums there. Hip-hop culture reached the mainstream in the 1990s, and Ms. Amarantos's style of music—a quick-paced, beat-heavy, highly danceable electronic sound—which itself dates only to the late 1990s, is now also finding wide acceptance. (Ms. Amarantos sings the theme song to a popular soap opera, and she recorded the official tune, "Todo Mundo," for the coming 2014 soccer World Cup in Brazil. In New York this week, she was tailed by an entourage that included a hair and makeup aide and a crew filming a documentary about her.) That's highly unusual for music conceived in Brazil's poor north.

"Even though Gaby's music is not political, the fact that she became a star singing a homegrown music from Belém, without having to become something else, is a political act in itself," Mr. Lemos said.

Some cultural critics have said that tecnobrega is the quintessential Brazilian music of its age, cannibalizing standards and styles, sampling and mixing foreign sounds with indigenous ones tied to themes of love, betrayal, happiness, tragedy and drunkenness, to make something uniquely Brazilian. An Amarantos cover of Beyoncé's "Single Ladies" earned her the moniker "Beyoncé of the Amazon."

Noteworthy, too, is the business model that Ms. Amarantos has helped spawn with tecnobrega, in which record companies and radio stations are rendered moot. Songwriters let DJs and producers pirate their music and distribute it cheaply on CDs, which helps popularize artists. The artists go on to earn fees when they perform at the street parties, which regularly attract thousands of people.

Not surprisingly, then, all three of Saturday's singers have played a role in Brazil's populist turbulence—not unlike the stars of the country's Tropicalia movement of the 1960s, when singers including Caetano Veloso and Gilberto Gil repudiated Brazil's dictatorship. "Of course, there isn't a dictatorship now, but one could speak of what some perceive to be a neoliberal and developmentalist dictatorship within democracy, with the government selling off public resources," said George Yudice, a University of Miami professor who has written about contemporary Brazilian music.

During his recent interview, Marcelo said that, two years ago, his grandmother died while he was on tour in Germany after she had a heart attack. She had gone to a hospital that had no doctors on call to help.

"This is a common problem in Brazil," said Marcelo, who sports a tattoo of his Brazilian musical hero, Bezerra da Silva, on his forearm. "It's about education, health. It's about corruption and impunity. Nobody is held responsible for their crimes. People are tired of this."