Margaret Juntwait in her radio booth at the Metropolitan Opera in 2011. (Jonathan Tichler/Metropolitan Opera via AP)

Margaret Juntwait, whose voice was known to millions of listeners whose great pleasure in life is not a night at the opera, but rather an afternoon beside the radio, died June 3 in Saddle River, N.J. She was 58 and, for the past decade, was host of the Metropolitan Opera’s Saturday matinee broadcasts.

The cause was ovarian cancer, said her husband, Jamie Katz.

In caricatures and cartoons, the opera often appears as entertainment for the elite, an art form favored by musical creatures whose natural habitat is the box seat. But beyond the diamond-bedecked and tuxedo-clad patrons are listeners who love the music without restraint, although they may never have heard an aria in person. They are patrons of the Met’s radio programming.

For more than 80 years, in an initiative now billed as the “longest-running continuous classical music program in radio history,” the New York City opera house has broadcast its Saturday matinee performances on stations around the globe.

Today an estimated 8.5 million listeners tune in for performances from the theater that is widely considered one of the best opera houses in the world. For the past 10 years — including 229 live Saturday broadcasts and 898 performances on the Met’s Sirius XM channel — Ms. Juntwait narrated the action onstage and in the pit, the curtain falls and curtain calls.

The Met broadcast its first Saturday matinee in 1931 as a fundraising initiative during the Depression. Since then, 13 U.S. presidents and seven popes have come and gone. In Italy, opera’s spiritual homeland, dozens of governments rose and fell. But the Met Saturday broadcasts, long underwritten by Texaco and now supported by Toll Brothers, had only three regular hosts.

The first was the venerable Milton Cross, who died in 1975 of an apparent heart attack while preparing for the next day’s performance of Rossini’s “L’Italiana in Algeri.” The second was Peter Allen, Cross’s former standby, who never missed a broadcast in his own 29 years as host. Ms. Juntwait succeeded Allen in 2004, making her Saturday debut in a performance of Verdi’s “I Vespri Siciliani.”

“It’s not a common career,” she once quipped.

Trained as a lyric soprano, Ms. Juntwait aspired to be an opera singer but found that the profession did not accommodate the demands of early motherhood. She sang at dinner theaters and churches, making most of her money at funerals, before beginning a broadcast career in 1991 at WNYC in New York.

At the Met, she was ensconced in a small radio booth behind the seats in the house’s highest tier, where she brought her listeners all the excitement of a performance, from the rising of the theater’s crystal chandeliers at showtime to the tinkling of champagne glasses at intermission to the thunderous final applause.

She credited Met researchers with feeding her “tidbits” about the musicals scores and performers, but the play-by-play fell to her.

“I listen to Yankee games on the radio with John Sterling or Suzyn Waldman,” she once told the Record newspaper in Bergen County, N.J. “I’m constantly getting ideas from them. Of course, not about content, but about what’s important to a listener. What do they want to know at any given time?”

Instead of sliding into home plate or stealing a base, Ms. Juntwait’s subjects hit nine high C’s or delivered fatal blows. She explained mistaken identities and misdirected letters with such clarity that, at times, her radio listeners might have followed the action better than the spectators in the theater.

“It’s very important to let the audience know what’s happening onstage as soon as the curtain goes up,” she told the Boston Globe. In Wagner’s “Tannhäuser,” she observed, “Venus wears a very low-cut gown. It’s slit way up her leg. She’s the goddess of love, and you have to let people know that!”

Margaret Ann Juntwait — the name is Norwegian — was born in Ridgewood, N.J., on March 18, 1957. She said she heard her first Met broadcast at the home of a classmate, whose mother enjoyed the opera.

A choir teacher inspired her interest in vocal music, and Ms. Juntwait graduated from the Manhattan School of Music in 1980. She got her WNYC job by writing a fan letter to a host who hired her as an assistant.

In the 10 years that she suffered from cancer, Ms. Juntwait missed only a single Saturday matinee broadcast, according to the Met. Her last Sirius broadcast was a performance of Lehar’s “The Merry Widow” on New Year’s Eve. The opera house has not announced a successor.

Ms. Juntwait’s marriage to Peter Andreacchi ended in divorce. Survivors include her husband of 13 years, Jamie Katz of New York City; three sons from her first marriage, Gregory Andreacchi of Brooklyn, Bart Andreacchi of Los Alamitos, Calif., and Steven Andreacchi of Jersey City; a stepdaughter, Joanna Katz of New York City; her mother, Florence Grace of Montvale, N.J.; two brothers; a half-sister; a half-brother; three stepsisters; a stepbrother; and two grandchildren.

Ms. Juntwait once told the New York Sun that she thought “everybody should be able to go to the Met and experience what a special place it is.” In her broadcasts, which came close to simulating the feeling, she had an uncanny ability to finish her sentence just as the music resumed.

“You have to become one with the performance,” she told the Record. “I actually sort of enjoy feeling that I’m riding the crest of the wave of what’s going on in the pit. . . . It’s like surfing. You’re riding the crest of momentum — the conductor, the sound of the applause.”