Cornell MacNeil, 88, an American baritone who was best known for his interpretations of operatic roles by Giuseppe Verdi and who once touched off a backstage melee at an Italian opera house, died July 15 at an assisted-living facility in Charlottesville. The cause of death was not disclosed.

Mr. MacNeil, who possessed a robust voice and a powerful stage presence, had modest success before leaping to operatic stardom in 1959. In the same month, he made triumphant debuts at La Scala in Milan and the Metropolitan Opera in New York — perhaps the two most prestigious opera stages in the world.

After appearing in Verdi’s “Ernani” at La Scala on March 5, 1959, he was summoned to substitute for an ailing Robert Merrill in the title role of Verdi’s “Rigoletto” at the Metropolitan Opera on March 21. Mr. MacNeil arrived in New York on the day of the performance, with only enough time to be fitted for a costume before the opening curtain.

“He went through the part as if he had been playing at the Met all his life,” critic Eric Salzman wrote in the New York Times. “When he cut loose, the rafters trembled.”

Over the next 28 years, Mr. MacNeil sang more than 600 times at the Met, including more than 100 performances of “Rigoletto.”

Music critic Winthrop Sar­geant wrote in the New Yorker in 1966 that Mr. MacNeil was “one of the truly great Rigolettos, with a voice of immense size and a fine grasp of character.”

He became equally renowned for his portrayals of Iago in Verdi’s “Otello,” Count di Luna in Verdi’s “Il Trovatore” and Scarpia, the malevolent police chief in Giacomo Puccini’s “Tosca.”

When he appeared in Washington in “Tosca” in 1978, Washington Post music critic Paul Hume wrote, “MacNeil’s Scarpia is menacing, sinister, lustful, and, in sum, genuinely vicious” — exactly the character Puccini intended.

Early in his career, the Minnesota-born MacNeil was not always comfortable with the conventions of opera. Before he mastered the Italian language, his gestures did not always match the lyrics he was singing.

By the 1960s, however, he had lived in Rome and had grown conversant in the Italian of the stage and street. He gave a rousing performance in 1963 at the Teatro Regio in Parma, known as “the lion’s pit of Italian opera” because of its notoriously critical audience.

There was prolonged applause, but Mr. MacNeil did not return to the stage to acknowledge it because, as he later explained, he didn’t want to “interrupt the dramatic flow of a piece by going out and taking a bow.”

A year later, during a performance of Verdi’s “Un Ballo in Maschera” on Dec. 26, 1964, the Parma audience continually hissed at a soprano, preventing Mr. MacNeil from singing a third-act aria.

“I was getting more and more angry as the rumbling and noise got worse,” he told the New York Times the next day. “Finally, I couldn’t stand it any longer.”

Using his newly fluent Italian, Mr. MacNeil shouted, “Basta, cretini!” (“That’s enough, idiots!”) and stormed off the stage.

A near-riot broke out backstage. As the staff tried to block Mr. MacNeil from leaving the theater, the stage manager punched him in the jaw.

After a series of lawsuits, Mr. MacNeil was required to return half of his performance fee.

Cornell MacNeil was born Sept. 24, 1922, in Minneapolis. His father was a dentist, his mother a singer. He told the New York Post in 1973, “I can’t remember when I didn’t sing.” He performed on radio at 12.

Severe asthma kept him out of the military during World War II.

When he decided not to go to college, his father stopped supporting him. Mr. MacNeil found work as a machinist at a Pratt & Whitney engine plant in Hartford, Conn., while studying at the nearby Hartt School conservatory.

He began to find small parts in musicals and summer-stock theater and made his operatic debut in 1950 in Gian Carlo Menotti’s “The Consul.” Mr. MacNeil was 30 before he gave up his job as a supervisor at a Bulova watch factory in New York to devote himself to opera.

He sang with the New York City Opera from 1953 to 1956, earning rapturous reviews, then traveled widely around the world before joining the Met in 1959. His final performance at the Met came in “Tosca” in 1987.

As president of the American Guild of Musical Artists, Mr. MacNeil represented performers in negotiations with the Met’s management for years.

In retirement, he lived in Toronto and Charlottesville, where he had an elaborate woodworking shop.

His first marriage, to singer Margaret Gavan, ended in divorce.

Survivors include his wife since 1972, violinist Tania Rudensky of Charlottesville; five children from his first marriage; two grandchildren; and three great-grandchildren.

In 2007, Mr. MacNeil described the surge of energy he felt when taking the stage.

“It’s the audience — the public — how it works on you and how you work on them,” he told Opera News. “There has to be an interchange of feeling. Everybody is trying . . . to make the public want to come back again. I felt that all the time.”