Last night's gala at the Kennedy Center ended the way such events are supposed to: A cascade of "bravos" hard on the heels of the last note, with the first "bravo" coming from the male section of the chorus; a dozen women from the audience rushing down to the stage with bouquets before ushers could bring the official bouquets out from the wings; a standing ovation that lasted (with interruptions for encores) more than 20 minutes. The purpose of the benefit gala was to raise money for renovation of the Opera House, but the sheer power of the applause threatened to blow down its walls.

Placido Domingo, aided considerably by conductor Julius Rudel, the Opera House Orchestra and the Choral Arts Society, had built the evening to a climax with consummate skill. Then the climax was topped when the orchestra swelled into the familiar opening bars of "Granada" for the second encore, and the crowd went wild before the great tenor could even open his mouth.

It was not at all sure, a few days ago, that the gala would have such a happy ending. Domingo, who rarely cancels a singing engagement, had been stricken with flu and canceled everything for two weeks, including the Metropolitan Opera. Last Friday night, he was absent from a black-tie dinner given in his honor at the Spanish Embassy, though by that time the prognosis had become cautiously optimistic. As it turned out, he not only sang but sang splendidly, his voice apparently refreshed by its enforced rest.

Sponsors of galas (which are becoming the dominant performing art of our time) face a choice between two basic strategies: diversification or tight focus--20 attractions performing for a few minutes each, or one big star to fill a whole evening. If you diversify, you can fill the hall with a combination of pop and classical fans, and it is not quite tragic if a few performers cancel at the last minute. The focused approach gives an evening more artistic coherence, but it can be terrifying when a sold-out house, complete with pre-concert reception and post-concert dinner, depends on the condition of a single tenor's throat. By coming through when he was needed, Domingo saved not only the evening but also the reputation of star tenors for reliability, which has become even more tattered in recent months than the velvet in the Opera House.

The strategy of the program was also risky, particularly in the first half, when the values of art were emphasized over those of entertainment a bit more than may be advisable on such occasions. Domingo carefully avoided the standard tenor crowd-pleasers ("La donn' e mobile," "Che gelida manina," "Vesti la giubba" and all that), choosing instead a solid program for connoisseurs that was a compliment to his audience as well as a tribute to his versatility. He began with the "Kleinzach" aria from "Tales of Hoffmann"--not a concert reduction but the whole sequence from the opera including the impassioned reverie that interrupts it.

It was a severe test, not at all the usual warmup piece that singers allow themselves on such programs, and it was done beautifully--crisp and funny at the beginning; then intensely romantic and, at the end, visibly determined to escape from obsession into comedy. Every nuance was precisely right, as they were in "O souverain" from Massenet's "Le Cid," the Brindisi from "Cavalleria Rusticana" and (after intermission) "Ah, la paterna mano" from Verdi's "Macbeth."

Domingo did not get into the tenor top-40 until well into the second half of the program, during the final sprint to the ovation, when he built "Recondita armonia" from "Tosca" to a climax as carefully as he was building the whole evening. Then (reading with precision the mood of the audience), he dropped a number from "The Gypsy Baron" and substituted "I'm Going to Maxim's" from "The Merry Widow." It was sung, in English and Spanish, with a lecherous languor that was exquisitely comic, and led into an unfamiliar but splendid romanza from a Spanish zarzuela that brought the formal program to a dazzling close.

It was very much Domingo's show, but not entirely. Rudel conducted with his usual proficiency and specialized knowledge of how to blend voice and orchestra. It was good to see the Opera House Orchestra on stage rather than in the pit, and the sound was enhanced by this more visible position--though more rehearsal would have done no harm. Norman Scribner's chorus sang superbly, as always, and the many choral and orchestral interludes in the program enhanced its variety while giving the singer breathing space between numbers. More than most of the galas that happen in this gala-rich city, this one seemed to show how it ought to be done.