"Once upon a time, there was a king," begins Cinderella's first aria in Rossini's opera, "Cenerentola." This simple, wistful number ("Una volta c'era un re"), with its hint of folk-song flavor, is practically the only touch of fantasy in the show, which is otherwise a savagely funny study of the seamy side of family life, raw greed and ambition, social pretension and stupid snobbery. But even without a fairy godmother, there is magic in the Washington Opera's new production, which opened last night in the Kennedy Center's Terrace Theater.

Much of the magic can be credited to the two Italian composers involved in this production: Gioacchino Rossini, who endowed it with a wealth of scintillating melody 155 years ago, and Gian Carlo Menotti, whose stage direction sparkles as brilliantly as the music. But magic pops up everywhere; it glows in half-a-dozen singers' performances, in the effervescent lilt of the orchestra's phrasing under Cal Stewart Kellogg, in Zack Brown's ingenious scenic designs and in the precise sounds and gestures of William Huckaby's chorus. It is the kind of magic that works best in the Terrace: a magic of small details and fine-tuned coordination, the magic of fine ensemble performance on an intimate scale.

Observed coldly and at a distance, "Cenerentola" is a rather silly story: Prince Charming (called Don Ramiro in this version) wants to find a woman who loves him not for his title and wealth but for himself, so he exchanges clothes and identities with his valet, Dandini, goes out wife-hunting and encounters Cinderella (alias Angelina), who is busy doing domestic chores while her mean sisters live in a seedy pretense of luxury. It is love at first sight (conveyed in a beautiful, hesitant duet, "Un soave non so che"), but it takes two more acts and several more twists of plot before they can both be sure that it is true love, and neither will settle for less.

What saves the mandatory love story from banality (besides the music) is the comic element, entrusted primarily to three highly skilled performers in this production: Franc,ois Loup as Don Magnifico, father of Cinderella; Melanie Helton and Joanna Levy as the daughters Clorinda and Tisbe, one of whom Magnifico expects to make him an ancestor of kings. In the comic dimension, Loup (who has been seen here previously as the sacristan in "Tosca" and in the title role of Offenbach's "Monsieur Choufleuri"), sparks the entire production. His face and hands are as expressive as his excellent bass voice, and he can sing a Rossini patter song with a delicacy that makes one wonder how he would be in Gilbert and Sullivan. He is superbly pompous in "Noi Don Magnifico," dictating a decree as superintendent of the royal wine cellar while the men of the chorus scramble around trying to make 6,000 copies. He becomes Falstaffian in a comic duel, where he is armed with a wine bottle against Dandini's stick; his dreams of glory and backstage power at court ("Gia mi par") could be simply a solo aria sung in front of the curtain to kill time while the scenery is being changed. But in Menotti's staging the aria is transformed into a one-man production number, supported by a long line of butlers who march across stage with food for the prince's banquet.

Levy (who was Mistress Quickly in "Falstaff" last month) gives a fine cameo performance as a spoiled, self-indulgent glutton who carries a spoon in her cleavage so that she can steal part of her sister's dessert, and who cannot hide her selfish feelings even when showing they can lead to disaster. Helton has a remarkable ability to look disgusted -- as though her nose has just encountered a bad odor -- which she exploits to the hilt for comic effect. Both sing well and act even better, presenting a united front against Cinderella but otherwise fighting viciously for advantage over one another in their pursuit of the prince.

Vocally, the outstanding member of the cast is Patricia Schuman in the title role, a mezzo whose upper register has the speed, accuracy and flexibility required by Rossini's demanding music. Her lower tones were clear and precise from the beginning but acquired more richness as she warmed up. Her second performance of "Una volta c'era un re," fairly late in the opera, was considerably better than the first at the beginning, though the first had been quite acceptable, and her fine performance of "Non piu mesta" at the end, supported by the ensemble, brought the work to a properly brilliant conclusion. In the role of the prince, tenor Gary Bennett had a bright, clear tone, a good sense of style in coloratura passages but sometimes incomplete control -- slight problems but occasionally perceptible. Allan Glassman was excellent in the relatively small role of Dandini, as was John Fiorito in that of Alidoro, the prince's tutor and primary manipulator of the plot.

Stellar individual performances were not the object of this production, however. There are many spectacular vocal passages, and they are properly sung, but the distinctive feature of this "Cenerentola" is the exquisite care given to ensemble singing (one of the opera's principal riches), as well as the recitatives, which are not hurried through (as happens so often) but carefully weighted and exploited for their dramatic value. The costumes are excellent, particularly the party dresses for Clorinda and Tisbe, which tip over ever so slightly from mere elaboration into vulgar ostentation. The sets rise above budget limitations, even in the palace scenes when the supposedly marble pillars made out of cloth sometimes sway slightly. Don Magnifico's home is particularly well done -- pretentious but decaying, with a landscape mural that is slowly peeling off the wall and a roof that leaks during the brief storm sequence. Such small details give the performance a special distinction.