SANTA FE, N.M. - It was an extraordinary notion: Turn this dusty hilltop outside a sleepy southwestern town into a destination for opera-lovers.

"Where's Santa Fe?" mezzo-soprano Regina Sarfaty Rickless remembers asking John Crosby when he invited her to join his fledgling company. "Why would you want to build an opera house in the desert?"

On opening night in July 1957, the 22-year-old New Yorker, making her professional debut as the servant Suzuki in Puccini's "Madame Butterfly," got her answer.

"The moon was a full moon and the back (of the stage) was completely open," Rickless recalled. "And when the Humming Chorus came and we closed the shoji screens, you could still see the moon in the background. It was heaven."

The wooden benches in the open-air opera house were filled - tickets ranged from $2.40 to $4.80 - and there were 10 curtain calls.

The Santa Fe Opera was on the map.

As it celebrates its 50th season this year, SFO has become the largest and most influential of American summer festivals, says Marc Scorca, president and chief executive officer of Opera America, the national service organization for opera. Its apprentice program for singers and technical staff, championing of new works and adherence to artistic excellence have put it at the forefront, he said.

Set in the foothills of the Sangre de Cristo Mountains, with the Jemez Mountains to the west providing stunning sunsets, it is "physically glorious" as well, he said.

"There is nothing like hearing the music, looking at the beautiful scenery and feeling the warm breeze off the desert. It adds yet another dimension to the sensual experience that is opera," Scorca said.

The 50th anniversary season, which runs through Aug. 26, reflects the mix that was Crosby's formula: a new production of Bizet's "Carmen" with Anne Sofie von Otter; a new production of Mozart's "The Magic Flute" with Natalie Dessay; a new production - and the first performance by SFO - of Massenet's "Cinderella" with Joyce DiDonato; a new production of Strauss's "Salome" with Janice Watson; and the American premiere of Thomas Ades' "The Tempest," with Cynthia Sieden.

Crosby, who died in 2002, was a musician and conductor from an Eastern family who had been sent to a boarding school in nearby Los Alamos because of his asthma.

Friends describe him as extremely shy, a stickler for detail and a financial genius.

He could tell you "how many spools of thread were in the costume shop and how much each one cost," said Thomas Catron, a Santa Fe lawyer who has been on the opera's board almost continuously since it began.

Catron remembers thinking an opera was "a great idea" - he had become a fan in Italy, after World War II - but he wasn't sure an out-of-the-way town of 25,000 was the ideal spot.

But Crosby "was very convincing … because he knew exactly what he wanted and how it would work," Catron said.

He had found a guest ranch - once a pig farm - on which to build a 500-seat theater. In the early years the young singers lived there as well, in the low, rambling ranch buildings that are still used as offices.

Rickless, who for $100 a week sang in five of the seven operas that first summer, remembers the coziness and camaraderie.

"We were all very young. Nobody was a known star. … They came here to hear an ensemble," she said.

That was part of Crosby's plan, says Richard Gaddes, the engaging, British-born general director who took over from Crosby six years ago. He wanted to create opportunities for American singers: For the first time, they wouldn't have to go to Europe in the summer to train and perform.

From the start, the opera company attracted attention - boosted by the recurring presence in the early years of Igor Stravinsky, whose "The Rake's Progress" was among the first year's productions.

"I can't think of a summer opera company with the cachet that Santa Fe had from its very beginning," Rickless said.

There also were challenges: soaking summer rains and occasional high winds, as well as the elevation. At 7,000-plus feet, the air is thin and dry and takes some getting used to.

"My nose bled. My lips swelled. You know, everybody had trouble," said Rickless, who returned to Santa Fe nine years ago after 36 years in Europe. She now lives right next to the opera grounds and coaches apprentices.

Mezzo-soprano DiDonato says it takes a full two weeks to get acclimated in Santa Fe, which she calls "just a magical, magical place to be."

"The good thing is, when you leave you always feel like you're singing like a goddess when you get back to sea level," she said.

DiDonato was an apprentice in 1995, which she said was invaluable for the experience and the exposure.

"It was my first time to stand next to professional opera singers," she said. "For a lot of the singers here it's the first time people in the business … put a voice with the name."

The opera house Crosby built burned to the ground in 1967. Within a couple of days, the company was performing in a high school gymnasium, where it spent the season.

"It was a remarkable coming-together of the community," said Catron, who has seen every opera the company has performed over its half-century.

The opera house was immediately rebuilt - although a big chunk of the audience still had no cover - and then remodeled again in 1998, giving it a high, sweeping roof that keeps opera-goers dry but still allows them to see the mountains and sky.

Gaddes has promoted other user-friendly features: electronic libretto in English and Spanish, earlier starting times, shuttle bus service, picnic suppers for tailgaters - the parking lot opens early so patrons can catch the sunsets - and informal talks before every performance. There have been offseason productions in local theaters, and two years ago the opera simulcast a sold-out performance of "La Sonnambula" with Dessay for free in a Santa Fe park.

"John Crosby believed that festivals were places of destination. … There had to be some unusual artistic offering that would attract people to make a special journey," Gaddes said.

At the same time, the Santa Fe Opera has tried to develop and keep a strong local base. Currently, at least half the audience is from New Mexico, up from 32 percent a decade ago.

"That was deliberate," Gaddes said. "You always have to watch … that you don't get branded as being elitist."

On the Net:

Santa Fe Opera, www.santafeopera.org