SEPT. 8, 1971: the grand opening of the Kennedy Center. In the Opera House, Leonard Bernstein's ambiious "Mass" premiered. Rose Kennedy presided. From Edward Kennedy to Alice Longworth, the politically and socially elite were there in force. It was the turning point for the performing arts in Washington.

And in the lead role as the Celebrant of "Mass," a 25-year-old baritone named Alan Titus, who not long before had been getting by as a surgical orderly at New York's Gracie Square Hospital, became an overnight star.

He took the audience by shock with his startling physical presence, his sweet voice and his combination of tenderness and zealousness. He seemed so right for Bernstein's theme -- the moral imperatives of the counterculture and the anti-war movement merging with the ritual of the Christian Mass. Titus held the stage with barely a break for two hours--from Bernstein's tender "A Simple Song" to the Celebrant's violent Mad Scene. It was a virtuoso performance.

Ever since, he has been trying to live up to that standard. As happens so often with early stardom, being the Celebrant proved for Titus a mixed blessing. It made him a celebrity, but it threw him off the course of the opera and recital career he wanted, and that he is now pursuing.

It is an old story in music, the prodigy who can't sustain his own level of success. The prime example, of course, was the greatest of musicians, Wolfgang Amadeus Mozart. And there are the brilliant creative figures whose bodies seem finally to rebel under the strain -- the Leon Fleishers and the Maria Callases.

But after some hard years, things are looking up for Alan Titus. Last Wednesday, he returned to the Kennedy Center to sing what he calls his "first major recital" in the Terrace Theater. And this Wednesday he will sing Sharpless in Puccini's "Madama Butterfly" on PBS' "Live From Lincoln Center."

Titus was both the beneficiary and the victim of quick media saturation. Not long before his performance in "Mass," he was learning to sing and existing on odd jobs. His wife, a fashion reporter for Women's Wear Daily, was the real breadwinner.

And even after he prevailed in the exhaustive weeding-out process for a leading man in "Mass," he was paid "under 4,000" for the six-week run.

"My teacher had advised me not to take the role, but I couldn't resist it," he recalls. "And after that something happened that I didn't expect. In fact, I wasn't prepared for much of anything that happened to me. 'Mass' turned out to be a boon to my image, but it didn't do much for my singing voice. And since 'Mass' was neither musical comedy nor opera, everybody knew my name but nobody knew what cubbyhole to put me in.

"Julius Rudel was at the Kennedy Center at the time and he heard me and he said I really wasn't mature enough to sing opera. I bristled. Meanwhile, my fee went up to $2,000 a performance, and I wasn't getting hired. And I felt my voice was not appreciated. I resented reviews that mentioned how good I looked.

"Finally, I had to take the best I could get. I went with Rudel and the New York City Opera, and started with the smallest part in a production of 'Summer and Smoke.' "

Today Titus is a busy lyric baritone with the City Opera. This season he is singing five roles. Today he opens their "Marriage of Figaro" as Count Almaviva (he sang the Count two summers ago at Glyndebourne, that English mecca of Mozart opera).

He can say now that he has come a long way. "The problem was that I had no experience. Opera was a frightening test for me and I felt inadequate. It was very daunting. In 1976 I went to San Francisco to make my debut as Papageno in 'The Magic Flute.' The critics said I was too slick. I didn't know the Mozart style.

"I was trying to change course. It was roughly that period that I had the most frustrating time. I thought of stepping out altogether. My wife was quite sick for a good while. And things were going so badly that I stuck to operetta.

"Meanwhile, I was starting to become a recital artist, under contract with Columbia Artists and going to small cities around the country. I used it to build my repertory and to be a springboard for recitals like the one at the Kennedy Center. I didn't just go to those places and do something from 'Carousel' and sing down to the audience."

And he set to work on his opera singing. "I learned that in Mozart much of the style is in the dynamics. As the Count, for instance, there must be growing tension, but you must not let it break through. It's like flamenco music. There are not many things these days from which you can get a concept of what 18th-century elegance really was. Maybe from a '45 Margaux? Anyway, it's very subtle and it can't be overdone."

Now that things are going well for Titus, would he ever do "Mass" again?

"Well, they asked me to for the Kennedy Center revival and I didn't want to," he says.

It is suggested that the part requires a certain youthful physical allure. Titus, who is about to turn 37 and has become somewhat thicker at the waist, agrees.

"It's like a lot of kids you see walking down the streets. They see that physical perfection is something that turns other people on sexually. They know that they're attractive. But by the time they begin to understand what it's all about they are beginning to lose it."

Will he ever play the Celebrant again?

"I don't think I could do it justice. For that sort of role I want to try Don Giovanni instead."