At the Metropolitan Opera, the drama begins before the first note is sounded, when audience members settle into their seats and a dozen crystal chandeliers ascend toward the gold-leaf ceiling in less than a minute and a half.

On December 11, radio listeners will hear a new voice recreating the magic of the theater over the airwaves. Margaret Juntwait, heard locally on WQXR 96.3 FM, and worldwide by 10 million, will cue the dimming of the Met lights and the official start of the radio season’s opening performance of Verdi’s “I Vespri Siciliani.”

“I hit a certain word in the script and the chandeliers start to go up,” Ms. Juntwait said, sitting before a backdrop of plants in the book-lined living room of the Inwood apartment she shares with her magazine-editor husband, Jamie Katz. “It’s very cool.”

The 47-year-old Ms. Juntwait, newly appointed Metropolitan Opera Saturday Afternoon Broadcast announcer, is about to make history as the third person and the first woman to “man the mike” on the nation’s longest-running radio cultural program.

Following in the footsteps of two legends, Milton Cross and Peter Allen, Ms. Juntwait will announce 20 performances sung in Italian, French, German, and Czech, by 13 composers, including three of four new productions: Handel’s “Rodelinda,” Mozart’s “Die Zauberflote,” and Gounod’s “Faust” this season.

Only the third regular announcer since 1931, Ms. Juntwait had been Mr. Allen’s backup for four years. His are “big shoes to fill,” she said. “He’s sort of like the Cal Ripken of radio broad casting. Cal Ripken never missed a game and Peter Allen never missed a broadcast.” Mr. Allen, who is in his 80s and retired last season, did the program for 29 years.

Although it turned out that she never needed to stand in for Mr. Allen, the Ridgewood, N.J., native is familiar to New York audiences. Since 2001, listeners have heard her weekend classical music radio program “Evening Music” on WNYC 93.9 FM, before that on the station’s afternoon music program, and on Sirius Satellite Radio.

No neophyte when it comes to live performance broadcasts, she has announced concerts at Zankel Hall and Avery Fisher Hall and PBS telecasts from the Met.

“They provide a script for me,” she said. “I provide the fill material. You never know how much you’ll need. If something about the set is awry, and they can’t give maestro the go-ahead, you need to fill in.” Her voice filled with excitement about Michael Griebel, the Met’s media librarian. “He’s just finding wonderful tidbits, like some unusual instrument being used in the orchestra or that someone performing is a new father or newly married.” She grinned and said, “He makes me a big table of information.”

One of four children growing up in suburban New Jersey, the blue-eyed broadcaster says theirs was “not a classical music household.” She heard her first Met broadcast at her best-friend’s house. “When I’d go over there to play, ” she recalled, her friend’s mom would have it tuned in. The operas “seemed very exotic,” she said. “My girlfriend and I,” decided that “the type of men we’d need

As a youngster who could sing, “I found myself involved in school choruses,” she said. “Once I was in high school, I was led to singing renaissance music.” After high school, she spent a year at St. Mary’s College in Indiana, before returning east. “I was homesick,” she said, “I just wanted to be at home where everybody loved me.” She transferred to Manhattan School of Music, where she commuted as a voice student, graduating in 1980.

“I got into opera sort of slowly,” said the lyric soprano. “What turned me on to it was singing.” At the conservatory, she considered herself “on track to become an opera singer. In other words,” she joked, “I had a church job.”

“My largest amount of income was singing at funerals,” she confided. “Shall My Soul Pass through Old Ire land” and “Come Back to Erin” were two favorites in her Irish-immigrant community.

” I never burned for it,” she said of a singing career. In 1982, two years out of college, she and her first husband had a son. “I had children early,” she said. A year later, she had twins. (Her oldest now 22, teaches English in France, and her other two sons are away at college.)

“When I realized I wasn’t going to be a big famous opera singer” she explained, she started to ask, “‘What else do I like?’ I had done a lot of dull jobs that didn’t mean a lot to me. I started to think ‘What else?'”

“I wrote a fan letter to John Schaefer,” she said of the WNYC radio host. As a church singer with lots of office skills from temping, she hinted that “If he ever needed an assistant,” she’d like the job. He did – part time. Although Mr. Schaefer insisted “the job was dull as dishwater” and consisted mainly of “typing his playlist,” she leaped at the opportunity. “The next day I got a call,” she said. A church wanted to hire her part-time. “We need a leader of song,” they said. In 1991, at age 34, her two part-time jobs were “divine intervention.”

“Once I got to WNYC, I stepped off the elevator on the 25th floor of the Municipal Building and I had a revelation that this was home,” she said. Assisting Mr. Schaefer, whom she called her “radio mentor” she said, “I was happy as anyone could be. I worked in his drafty office in the middle of winter, with my coat and mittens on, typing his playlist, and I couldn’t have been happier.”

Although Ms. Juntwait’s gig is one of the best in classical music radio, her new office is similarly humble. The exact location of the broadcast booth at the Met puzzles many. Some insist that it’s nestled in the rear of the orchestra level. Even a 20-year Met staffer did a couple of U-turns recently before honing in on its Grand Tier location.It takes up less room than a walk-in closet.

“When they shut the doors, it feels like you’re in a sound lock,” Ms. Juntwait said. “It’s almost comforting. You feel very safe in this little box.” It contains a chair, but Ms. Juntwait, like Mr. Allen, plans to stand. “It keeps the energy up,” she said. A small window, with a black curtain, looks past seats on the Grand Tier and down onto the stage. “We’ve joked about hanging Chintz curtains,” she admitted.

“Sometimes I’m waiting around before doing an opera,” she said. “Hearing the clanging of plates in the Grand Tier restaurant, the vacuuming of the rugs, seeing bartenders putting up the glasses for Champagne, I get a feeling about how lucky I am to be in this extremely lovely place. I love the smell of the soap in the ladies room. I just get so happy when I’m there. I want to share this with the radio audience. I think everybody should be able to go to the Met and experience what a special place it is.”