Much has been made in recent years of regional theater, and of how the emergence of these institutions since World War II has at long last given actors, playwrights and audiences a stable, stimulating alternative to Broadway and its tributaries.

But in this city, the talk is more about regional opera, and of how in the last two decades companies like the Seattle Opera have developed along the lines of regional theater as full-time, vital second choices to those traditional, high-budget giants like the Metropolitan and the San Francisco operas.

The Seattle Opera today finishes its seventh annual Pacific Northwest Wagner festival, in which there are two performances of each of the four operas of "The Ring of the Nibelung," the epic tale of how the ancient gods chartered their onw doom by betraying the social values chartered their onw doom by betraying the social values they were pledged to protect. In the century since Wagner finished "The Ring," it has become indelibly tied in the public consciousness with Germany own catastrophic wars of expansion and decimation.

Seattle's "Ring" is the most audacious, and widely publicized, single event in American regional opera. Whereas most regional opera, including the Washington Opera, is keyed primarily to a local audience, the Wagner festival plays to the visitor; about 60 percent of the listeners come from outside. This year there have been tour groups from Germany and Japan. Also, large numbers have arrived from the East Coast, which has suffered a "Ring" drought in the last decade. Because of casting and labor problems, the Met has been unable to mount its own "Ring," and no one else is equipped to do one.

Probably the only other spot this summer where one can hear in so short a period the 18-hour "Ring" operas -- "Das Rheingold," Die Walkure," "Siegfried," and "Gotterdammerung" -- is at Wagner's own self-made temple to his art at Bayreuth in Bavaria. The Seattle Opera's founder and general director, Glynn Ross, believes strongly in the Bayreuth-derived conception of the spirituality of "The Ring." When he opened the second "Ring" cycle on Tuesday night, the audience was welcomed to "the celebration of "The Ring.'"

In a recent interview, Ross, who started out intending to be an actor, compared Wagnerian opera to the Greek theater, "with its varying degrees of intensity. All that was needed to be added was the orchestra. The essential material in both cases is the subliminal relationship of myth, based in religion. Seeing "The Ring' needs to be one contiguous experience, like sex.

"The reason the audience will stand up and applaud for 20 minutes after a performance is not because of the theatrical experience but because of withdrawal pains. This is why the people in Seattle are less likely to sense this than the visitors, because they have to get up and go to work the next morning."

Lest this rhetoric sound a bit remote from reality in Seattle, it should be made clear that the Seattle Opera is one of the most popular institutions ever to take root here, in the 17 years since Ross started out almost from scratch. There is a lengthy winter season, with live operas, performed six times each. And a recent survey showed that Seattle has now developed an opera audience that is the highest per capita in the country. Retailers derive more than $600,000 a year from the summer visitors.

And several years ago, the city was alarmed at the thought of losing the opera company from downtown when there was talk of moving from the civic auditorium built on the grounds of the 1962 Seattle World's Fair. As an inducement to keep the opera there, the city passed a $600,000 bond issue that allowed air conditioning and expansion of the orchestra pit to better accommodate the 96-member orchestra. The large ensemble that plays in what is now called the Opera House is the Seattle Symphony, and its participation is an arrangement that has been impossible to duplicate in Washington because labor agreements prelude use of the National Symphony with the Washington Opera. Wagner normally sounds anemic with a reduced orchestra in anything but a small house. Seattle's is a little over 3,000, "and we've got everything they've got at Bayreuth except a fifth harp and a few more violins," says publicity director Galen Johnson.

In the short histories of our now numerous regional opera companies, the ones that have made the greatest gains are those that particularly excelled at building audiences while also building their reputations -- with adventurous casting and repertory that attracted notice throughout the arts scene. Luck, determination and ingenuity were also indispensable. Surely it is no accident that the companies to make the biggest splashes so far all developed under single, strong-willed directors -- Ross' Seattle company, Sarah Caldwell's Boston company, John Crosby's Santa Fe Opera and David Gockley's Houston Grand Opera.

Some might argue that the Washington Opera, an older company, also belongs in this grouping. But while it has produced many excellent productions, including several from the past season, repeated changes at the helm have created a blurred image, lack of momentum in development and thwarted impact.

Consider, for instance, these figures: In their most recent fiscal year, Seattle spent $3.6 million and Washington $3.3 million. But the Washington Opera's attendance was 42,500, less than a third of Seattle's. Metropolitan Seattle is about half the size of metropolitan Washington.

Ross had repeatedly cajoled, begged and bargained with singers, designers and grant-givers to get more for his buck.

"An artist," Ross says, "wants four things: one, a chance to do something that requires the best of his ability; two, the opportunity to grow by singing different roles; three, prestige; and four, a paycheck."

Bending these considerations, Ross will negotiate, with the implication that it's all a big favor, to get what he wants.

He goes after the stars with the second item on his list, offering them a special opportunity that bigger houses may avoid. That's how he got Juan Sutherland to sing "Lakme" here in 1967. He argued that there was no good recording, and that coming to Seattle would give her a chance to get ready for one, which she made the next year. Even in those days, Sutherland and her husband, conductor Richard Bonynge, commanded $16,000, but it was worth the money for the prestige brought to the then-fledgling Seattle company.

Likewise, he will hire promising singers on the way up for major roles that will help ready them for a chance at singing the same parts in larger, and richer, companies.

Just that is happening now for Wagnerian soprano Ute Vinzing, who has been the Brunnhilde in "The Ring" since 1977, as well as the splendid Isolde in this summerhs new "Tristan." She will be making her Met debut as Brunnhilde in the coming season. "But there's a dark side to that too," noted one official, "because going to the Met will make her want to raise her fee all the more for us. I don't know if we'll be able to afford it or not." Travel expenses alone for bringing German singers here have doubled in two years and the present favorable balance of payments to the United States has caused some of the singers to demand better exchanges on the mark.

In the summer "Tristan," Vinzing replaced the American soprano Johanna Meier, who was Isolde in the production debut last winter, but who could not return because now she is singing Isolde for the first time at Bayreuth.

Ross cajoles audiences with similar resourcefulness. In each winter season, he schedules solid mainstream works, some show biz and, ideally, something newsworthy and novel. This year the novelty was to have been the American stage debut of "King Roger," by the late Polsih composer Karl Szymanowski. But the project had to be delayed because of negotiating snags with the Poles over the star singer. Since each far-out endeavors are not exactly the kinds of things trustees press one to perform, Ross decided, "If we can't do it right, what's the point in doing it at all?"

So, next season will open with Strauss' "Die Fledermaus," with such supporting stars as Buddy Hackett, Miss America Susan Powell and Werner Klemperer, television's Col. Klink. Then there's Puccini's "Turandot" (which Birgit Nilsson once did for Seattle), Verdi's "Rigoletto," Mozart's "The Abduction from the Seraglio" and Puccini's "Madama Butterfly."

Just as with "The Ring," each opera sung in a foreign language will be repeated in English.

"The Ring" is done twice during the current two-week summer festival, the first in German, and the second in English, with younger singers replacing experienced ones who won't tackle New Yorker critic Andrew Porter's idiomatic translation. Two of this year's German singers are doing both cycles, with tenor Wilfried Plate's diction, in the role of Mime, better than that of most of his English-speaking colleagues. It's the German version that always sells out first.

In the winter, each foreign-language opera is done four times in the original and twice in English. Prices are cut for the English versions, with a single subscription costing as little as $22.50. But it's not so cheap for "The Ring." The top for the English series is still $44 a seat.

The state of the economy has dealt the Seattle Opera as unexpectedly large deficit, and a third of the administrative jobs have been eliminated, along with cancellation of the educational program.

But Ross keeps building. A new production of the entire "Ring" is "more and more likely" for 1983 and money is being raised for the first Seattle "Parsifal."

So much for the demise of provincialism.