Johnny Ventura, the singer, bandleader, composer and arranger who shaped the sound of modern merengue in the 1960s, keeping its tropical rhythms while speeding up the tempos and borrowing from rock ’n’ roll, died on July 28 in Santiago, the Dominican Republic. He was 81.

The cause was heart failure, the Medical Union Clinic in Santiago said in a statement. Mr. Ventura had been eating lunch when he suffered chest pains, collapsed and was unresponsive to C.P.R., the clinic said.

Often called “the Elvis of Merengue” and “the Black Horse,” Mr. Ventura released more than 100 albums over six decades, recording exuberant hit songs like “Patacón Pisao,” “Pitaste,” and “Merenguero Hasta la Tambora.” He won six Latin Grammys, including a lifetime achievement award in 2006.

But music was not his only pursuit. Later in life he became a businessman, earned a law degree and entered politics, serving as mayor of his country’s capital, Santo Domingo.

He was born Juan de Dios Ventura Soriano in Santo Domingo on March 8, 1940. As a young man from a family of modest means, he studied to become a secretary, hoping that an office job would help finance university training to become an architect. But after he won a radio talent contest for singing in 1956, he focused on music, graduating from the Hector J. Diaz school of broadcasting.

In his youth, the Dominican Republic was ruled by the dictator Rafael Trujillo, who promoted merengue, a rural genre, as a symbol of Dominican identity. “But there came a time when it became stagnant,” Mr. Ventura said in a 2016 interview with the newspaper El Tiempo, “because artists and groups wanted to dedicate most of their work to the boss.”

After Trujillo was assassinated in 1961, merengue began expressing a new sense of freedom, embracing unfettered tempos and uncensored lyrics.

“When Trujillo died, a political euphoria swept the Dominican Republic,” Mr. Ventura told Paul Austerlitz for the book “Merengue: Dominican Music and Dominican Identity” (2021), “and as youths of 21 years, we naturally participated in this.”

Mr. Ventura started out playing saxophone, but soon discovered that his natural talent was as a baritone singer. Tall and handsome, he was a charismatic frontman. He sang lead vocals on the biggest Dominican hit of 1962, Luis Peréz’s “La agarradera,” an up-tempo song full of double entendres.

By 1964 he had started his own band, Johnny Ventura and the Combo Show. Since young Dominicans were increasingly listening to rock ’n’ roll and salsa, he updated the merengue sound, incorporating those influences.

“Traditional merengue was completely identified with the tyranny and had been usurped by the enormous popularity that rock ’n’ roll had awakened in Dominican youth,” Mr. Venturawrote in a 1978 essay.

He made the Combo Show’s performances into visual spectacles, dancing with such abandon that he was compared to Elvis Presley — a comparison he encouraged by dressing like the American singer and even adopting his trademark smirk. Mr. Ventura appeared regularly on daytime variety shows and even hosted his own game show.

He began playing in New York City in 1967, finding success with American audiences and also recording duets with salsa stars of the day. He became particularly close to Celia Cruz, he said, singing with her and looking up to her as if she were an older sister.

As disco became the international sound of the dance floor in the 1970s, Mr. Ventura had to reckon with its popularity. “We incorporated almost all of the Bee Gees’ songs into the repertoire of my band, and the public applauded a lot when we sang those songs in English,” he told Mr. Austerlitz.

But simulating disco hits made him feel ridiculous, he said, “because I was accustomed to creating, always creating songs, and modifying merengue.”

“So I discovered that the basis of disco was in the beat of the bass drum,” he said. “That’s where the attraction was to the young people. So I began to use the bass drum in merengue, and the young people went back to dancing merengue.” The bass drum became a staple of the merengue sound.

Mr. Ventura returned to his studies while recording and touring, earning a law degree from the University of the Third Age in Santo Domingo, graduating summa cum laude. He dissolved his band in 1992 so that he could devote more time to his career as a distributor of Amway health and beauty products.

He served as vice mayor of Santo Domingo from 1994 to 1998, a position he described to The New York Times in 1999 as “almost decorative.” But when José Francisco Peña Gomez, his friend and colleague in the Dominican Revolutionary Party, died of cancer in the middle of a mayoral campaign, Mr. Ventura took his place in the election and won. He was mayor from 1998 to 2002, shoehorning in a live performance now and then.

As mayor, he wrestled with a housing shortage, woefully inadequate garbage collection and the various other needs of the city’s three million people. “People don’t think their problem will be solved unless they see the mayor,” he told The Times.

After his term as mayor, he said, he just wanted to play with his grandchildren, but he remained involved in politics — even running for mayor again in 2020, unsuccessfully this time, with the People’s Force party. “What does an artist have that does not allow him to be part of the solutions to his country’s problems?” he asked in an interview on television.

Mr. Ventura was married for more than 50 years to Nelly Josefina Flores. He is survived by her, as well as seven children, Jandy Ventura, Ana Yahaira Ventura Flores, Juan José Ventura Flores, Daysi Ventura, Erudi Andreina Ventura, Hilda Ventura and Virginia del Carmen Ventura; 17 grandchildren; and three great-grandchildren.

He was hospitalized in March 2020 after testing positive for Covid-19, but recovered and had announced plans for live concerts in the coming months. Only hours before his death, he posted on Instagram a video of himself dancing with a fan. In the caption, he wrote, “I miss the human warmth of my audience.”