BALTIMORE -- At twilight, they come from all directions.

A lawyer, a pediatrician, a librarian, an air-conditioning repairman, a retired Army major, a TV cameraman, a legislative aide to an Ohio congressman and even a newspaper columnist all have been converging on a north Baltimore prep school's auditorium for the past month.

Bitten by the show business bug, they and more than 100 other people of diverse backgrounds assemble to slake their theatrical thirst as part of Baltimore's Young Victorian Theater Company. They are the keepers of the flame for the ever-faithful devotees of Gilbert and Sullivan operetta.

For several weeks, after their normal routines, they have been immersing themselves in the glamor of life on the stage, putting long hours into learning songs and dances and making costumes and scenery. Tomorrow and on seven more evenings this month, they'll perform "The Yeomen of the Guard," the most elaborate and challenging of Gilbert and Sullivan's works.

"I enjoy the people up there," said Joe Metzger, 51, a craggy-faced, bearded installer and repairer of climate control equipment for Capitol Heating and Air Conditioning in south Baltimore. "There are all kinds of people. Men my age, well-to-do businessmen, boys from rich families, some obviously well-to-do, but they don't flaunt it. I'm from a blue-collar background, but they all seem to be nice people.

"This is something I was scared to do in high school. I was too timid. But I like to sing."

Metzger was recruited to join the company by his church choir director, J. Ernest Green, a doctoral candidate at the Peabody Conservatory who also is the Young Vic's music director and conductor of the 25-piece orchestra.

This year Metzger is cast as one of the Beefeaters who guard the Tower of London in "Yeomen," which is a tragicomic love story set in 16th century England and centered on the tower.

The Young Vic -- a semiprofessional, nonprofit company that technically is a department of Baltimore's Gilman School (which handles the ticket sales) -- began with a successful Gilman senior class production of "The Mikado" in 1971, followed by a summertime performance of "Iolanthe" starring Bess Armstrong, who since has become a star of such films as "The Four Seasons" and "High Road to China."

It has developed a reputation for ambitious, slick productions and has begun attracting more mature, semiprofessional and professional performers.

The lead singers, often graduates of such schools as the Philadelphia Academy of Vocal Arts or choral veterans of the Washington or Baltimore operas, are paid $100 to $1,000 per production, depending on experience and whether they have to travel. The company's full-time staff -- the managers, directors, costume designers and musicians -- also receive modest pay.

Amateurs, however, still make up most of Young Vic's cast and crew.

"There's a wonderful sense of humor that permeates the company," said Virginia Drake, 35, a cataloguing coordinator at the Milton S. Eisenhower Library at Johns Hopkins University, a four-year veteran of the Washington Opera Chorus, and one of the Young Vic's lead mezzo-sopranos.

"It's never so serious that you can't pull a practical joke on someone. All kinds of trash goes on in the chorus -- letting the backs out of people's pants, switching wigs, changing the words in rehearsal -- the sort of things that if you did them in a big-deal company would get you fired.

"Most of these kids sing for nothing and they have a right to have fun. And in the end, the show comes out first-rate anyway . . . because everyone is completely dedicated. If they weren't, they wouldn't be here. We do it because we love it and it's fun."

The ages of the Young Vic's thespians range from 16 to 60, and many members of the group say they prize the lack of any generation gap or professional envy.

"They've been very successful at creating an atmosphere that is pretty free of temperament and ego and all that kind of nonsense you sometimes have to put up with," said Steve Bailey, a baritone and sometime-tenor who spends his daylight hours as the legislative director for Rep. Don Pease (D-Ohio).

Mark McGrath, a cameraman for WBAL-TV, Baltimore's CBS affiliate, and a member of the Baltimore Symphony Chorus, cites a "love of the theater and the music" as one of the reasons he has been a member of the Young Vic for five years. But he also relishes "the camaraderie" in the company, "the sheer joy of getting together and putting on a show."

"When we left college, we left behind the opportunity to get together with people on a spontaneous basis," said McGrath, 30. "We may get together with friends after work for a beer or two, but everyone is still pretty much a workaday person." At the Young Vic, "we seem to put more into our personal friendships," he said.

Kathryn Arnold, 34, a former member of the Washington Opera chorus, is exuberant in her comments about the fun of singing Gilbert and Sullivan in the Young Vic productions. She even sang in an opening night performance of "HMS Pinafore" in 1985 when she was expecting a baby. At the cast party afterward, she went into labor and was rushed to a hospital, where she gave birth to her son, which is "another reason why it has a special meaning for me," she said with a chuckle.

The "spirit" of the company is "really quite amazing," according to Jerry Peterson, 46, a retired Army intelligence officer who spent 22 years in the service and is working his first season as the Young Vic's technical director.

"This group is quite unique. It gets together such quality professionals and amateurs and no distinctions are made between them," he said. "I think the most compelling thing about amateur theater as a hobby is that it is where young people and older people get together -- all pulling together -- to accomplish something."

Of course, in accomplishing that something, they earn applause, what one amateur, Baltimore Evening Sun columnist Dan Rodricks, called "the crowning glory to this summer fantasy."

"I enjoy getting on stage and singing," Joe Metzger said. "I like to be able to get in front of people and say, 'See, I'm singing. How about that?'