If the trousers fit ...

American mezzo-soprano Vivica Genaux and Spanish soprano Maria Bayo have only one scene together in “Orfeo ed Euridice,” Los Angeles Opera’s new production of Christoph Willibald Gluck’s 1762 opera.

But that scene tells the whole story.

According to the Greek myth of Orpheus (here, Orfeo), his wife, Euridice, dies of a snakebite shortly after their marriage. The musician Orfeo begs the gods to allow him to reclaim Euridice from the underworld to live out her natural life, arguing that they will get her back in due time. Charmed by the hypnotic beauty of Orfeo’s lyre, the gods grant his wish, on one condition: Orfeo must lead Euridice back from Purgatory into the upper air without once turning back to look at her.

Euridice “is probably one of the shortest roles I’ve ever had, but one of the most intense,” Bayo said this month as she and Genaux sat at a conference table in L.A. Opera general director Placido Domingo’s office in the Dorothy Chandler Pavilion. “It’s a magnificent scene for the both of us. But the scene lasts maybe 20 minutes, and then I leave.”

By contrast, Genaux’s Orfeo spends virtually the entire two-hour running time of the opera -- which opened Saturday night -- on stage, tortured by the conundrum of his assigned task. “It’s a different kind of pacing, because you don’t have time to go offstage and spit,” the mezzo said with a laugh, adding more soberly, “The big challenge of this piece, of course, is that I can’t look at her -- it’s a love story where I can’t look at her.”

In the L.A. Opera production, directed by choreographer and dancer Lucinda Childs, Genaux, 34, in the so-called trouser role of Orfeo, and the 45-year-old Bayo as Euridice are often surrounded by whirling dancers and a chorus of singers representing the Furies in Purgatory. Making occasional appearances above their heads -- floating on a giant ball that is the airborne centerpiece of Tobias Hoheisel’s set design -- is Italian soprano Carmen Giannattasio as Amor, the god of love.

Still, this drama is mainly fueled by the power of the passion between Orfeo and Euridice, and the two singers proved more than willing to discuss how two contemporary women hailing from different parts of the world, meeting each other for the first time, go about evincing the exalted love of a man and woman from Greek mythology in a 241-year-old opera sung in Italian -- in 20 minutes.

An interpreter was brought in to translate for Bayo, who speaks little English. The singers joked about the confusing blend of English, French, Spanish and Italian that flies around the rehearsal stage as the members of the multinational cast and crew try to communicate with one another. But although at the time of the conversation they had had only one rehearsal, they were already quite certain their Orfeo and Euridice were speaking the same language.

In real life, they share having been nominated for Grammy Awards in the best classical performer category: Genaux in 2003 for “Arias for Farinelli,” a collection of music composed for the 18th century castrato, and Bayo for a recording of Handel arias in 2001. Both also have a long association with singing Baroque music; Bayo has a coming CD of little-known Baroque zarzuela music.

Gluck’s “Orfeo,” while of the Baroque period, is noted for breaking with Baroque tradition by eliminating extreme ornamentation and offering a “through-composed” opera, in which musical patterns do not repeat and the music is driven by the text, like theater. “Gluck was very revolutionary in his time,” Genaux observed.

Because of her larger role in the opera, the mezzo, a native of Fairbanks, Alaska, had arrived two weeks prior to the conversation to begin rehearsals. Bayo had flown in just the day before. By chance, they had chosen fashion looks that fit their stage roles: The tall, angular Genaux wore chunk-heeled shoes, a turtleneck sweater and tight leather jeans; the petite, curvaceous Bayo had selected an ultrafeminine combination of dainty black boots with tiny tapered heels, a black-and-white print skirt and a bright orange sweater tied at the waist.

Genaux had had prior experience of hearing Bayo sing, at the Theatre des Champs Elysees in Paris. “She has a lot of different colors in her voice that she can call on,” Genaux said. “When I heard her singing Baroque music, she had not only so many different volume levels but color levels. That is her language, so many textures -- I love that.”

Bayo was not so ready with a description of her colleague’s voice. “I only heard her yesterday!” she exclaimed. “But one thing that is positive for me is that both voices work together well. There is a natural instinct here that really works.”

Two women portraying a man and a woman, while unusual in contemporary drama, is standard in opera. Many roles once sung by male castrati have been taken over by women. “I have about 17 trouser roles in my repertoire right now,” Genaux said. “I’m a mezzo, and it goes along with the mezzo territory. It also depends a lot on your temperament, how the voice sits and your physicality.

“I like trouser roles really well, because it gives you a chance to be a little bit more direct, in your actions and in your thought processes. The mezzo often tends to be a very powerful character type. Often she is the one who is getting everybody else into trouble, which I enjoy very much. In the women’s roles, you have to be so much more conniving and manipulative, whereas in the masculine roles you get to be so much more direct.”

Genaux added with another laugh that having grown up in Alaska has served her well in achieving the physicality necessary to slip easily into male roles. “You have to be able to get out of a car and change a tire when it’s 5 below and get moving,” she said. “I grew up being a kind of tomboy or barbarian or something -- my relatives all thought I was completely uncivilized.”

Bayo has also sung roles that were originally written for castrati, but she noted that the parts that fall in a soprano’s range usually were female characters, only sung by castrati because, at the point in history they were written, society would not accept female singers on stage.

Yet both women agreed that, particularly in the larger-than-life world of opera, the notions of male and female are more abstract than literal. “It’s not like being Hilary Swank doing ‘Boys Don’t Cry,’ ” Genaux said. “I approach it more as just being human. You accept your masculine and your feminine sides. It’s not as black and white as most people think it is.”

Genaux described her Orfeo costume, a sort of long frock coat, as something out of a Dickens novel that would also not seem out of place in “The Matrix.” She swooped through rehearsals in a black overcoat to capture the mood. At one rehearsal, director Childs said she too was trying to avoid pandering to stereotypes. “Of course it’s two women, and there’s the question of the body language. But I think of Vivica as Orfeo. It doesn’t have to be sort of defined as looking at a woman playing a man,” she said.

Neither Bayo nor Genaux intended to become an opera singer. Bayo planned to study classical guitar but found that there were no spaces for guitarists at the music conservatory she enrolled in, so she took up voice instead. Genaux studied genetics. “I was just miserable, mis-er-a-ble. So I decided that if I was going to be unhappy, I would go into music and be a starving artist,” she said. “And fortunately, it changed everything.”

Both also got their early musical inspiration from their mothers -- sort of. Bayo, who grew up in a Spanish town of 3,000, remembers her mother singing while going about her household chores. “For a baby or a teenager, the fact that your mother sings at home really has to influence you a lot,” she said.

“My mother used to sing too when I was little,” Genaux recalled. “But I would put both of my hands on both sides of her face and say, ‘Mommy, please don’t sing. You’re out of tune.’ Poor Mom, she tried.”

Bayo reacted merrily to that. “My mother used to say, ‘I know I am out of tune -- but I like to sing, so I’ll sing anyway,’ ” she said.

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‘Orfeo ed Euridice’

Where: Dorothy Chandler Pavilion, 135 N. Grand Ave., Los Angeles

When: Wednesday, Dec. 10, 13 and 19, 7:30 p.m.;

Dec. 6 and 21, 2 p.m.

Price: $25-$170

Contact: (213) 365-3500