Elegant in appearance, sumptuously garbed and generous with gods and goddesses, Handel's "Semele" made a dazzling vehicle Wednesday night for the Washington Opera's initiation of the Kennedy Center's Terrace Theater into the world of the baroque. Had the musical side of things equaled the visual, it would have been a great evening.

There are reasons enough for the relative scarcity of Handel's operas -- the greatest works of their kind -- on our stages today. The chief one is the problem of what to do in the A -- B -- A arias when the action sometimes ceases while the singer sings the A section the second time. Let us then praise stage director John Copley for his astute imagination in completely overcoming this hazard. Time after time, he found ways of creating new and reasonable movement for the singers while letting the audience enjoy hearing over again some of Handel's most beautiful writing.

Copley was fortunate in having gorgeously luxuriant sets and costumes by Zack Brown in which to move his cast. Often the Terrace Theater stage, enriched by Christine Wopat's exquisite lighting, took on the soft beauty of sensuous Georgian painting. But it was Copley's feeling for the drama of the piece, from the pageantry that began with the overture to Apollo's final tableau, that continually gave life to the elegant scenes.

The musical side of things was highly variable. "Semele" has a rich array of Handelian arias in every baroque manner: the cantilena, the character, and those demanding the utmost in bravura agility. In general, the slower, legato arias were the most successful, though there were some in the audience who rewarded several singers with much misplaced enthusiasm following the showier pieces.

Conductor Stephen Simon worked well to achieve the spirit of the music, blessed with impeccable playing of the essential harpsichord in the hands of Reilly Lewis. The orchestra was ragged much of the first act, out of tune at the beginning of the third, and variably rougher or smoother in between. It rarely sounded first-class, though Lewis and the continuo players added strengths and beauties to the eloquent recitatives.

Noelle Rogers sang the title role, looking the part for her bewitching aria, "Myself I shall adore." Her voice was often lovely, but as often showed signs of distress. The top C's and D were too much for her, and she lacks the degree of flexibility required for "No, no, I'll take no less." It may be a mark of what was missing in her singing that her most famous aria, "Oh sleep, why dost thou leave me?" won her no applause.

Her immortal love, Jove, was well sung by Alan Kays. Ideal in appearance, he came nearest of anyone in the cast to meeting Handel's superhuman demands in coloratura. But what happened to the composer's explicit direction that "Where'er you walk" be sung "pianissimo throughout"? It would also seem appropriate that Jove's final appearance, in his godly form, should blind both Semele and the audience in its brilliance. It was underdone.

Mariana Paunova, in the double roles of Juno and Ino, sang with rich sound, but few of her words could be understood, a crime in the clarity of the theater. Nor did Paunova, much admired in Verdi, find Handel conquerable at high speed. William Powers was an admirable Cadmus, Sunny Joy Langton equally so with no little brilliance as Iris. Drew Minter's countertenor served with elegance in both technique and sound as Athamas, and Stanley Cornett was excellent in the cameo role of Apollo. Somnus, the god of sleep, must, like Brunnhilde in "Siegfried," wait through a long sleep before making his appearance in the last act. Noel Tyl looked wonderful in the part, one of Handel's few comic roles. His voice was suitably gravelly, but not in the best shape.

It is quite possible, in the face of the heavy demands of the opera, that some of the singers were fatigued on opening night. The five repetitions scheduled through the next 10 days may find them in more assured estate.