THE WASHINGTON Opera's production of Massenet's "Cendrillon" (Cinderella), which opened at the Kennedy Center's Opera House Saturday, rounds out a season of marvelous musical theater with an evening of pure magic.

Magic, of course, is what this fairy tale is all about, and the details that have delighted children the world over abound in this production. There is a fairy godmother and her attendants who appear and disappear, a wondrous coach, and tattered clothing that is miraculously transformed into a glorious ball gown. But above all, there is the satisfying humbling of a nasty stepmother and her equally nasty pair of daughters by the good and modest Cinderella.

Credit for these delights must be shared by every aspect of the production. There are no weaknesses anywhere. Frederica von Stade's Cendrillon is vocally glorious and dramatically touching. She projects effortlessly, and she revels in the colorful shading of vowels that makes French such a sensuous language to sing.

Joyce Castle, Carol Sparrow and Luretta Bybee are outrageously funny as the stepmother and her two daughters who terrorize the servants and appall the lovesick prince. Jan Opalach as Cinderella's father straddles the line between a comic role as the stepmother's foil and a serious role as Cinderella's advocate with convincing vocal and dramatic skill. Tracy Dahl, whose voice is rather thin and reedy, nevertheless handles the fairy godmother's coloratura with accuracy and agility. Susanne Mentzer as the prince awakens splendidly from ennui to ardor, and Adolfo Llorca, Alan Held and James Ramlet are properly funny as hapless court personages.

One of the most appealing aspects of this production is its good-natured energy. Director and choreographer Brian Macdonald's dancers fill the ballroom scenes with a comic elegance that is never cluttered or frantic. The stepmother and daughters are dressed for the ball in one of theater's more marvelously conceived scenes, full of bustle and awkwardness, with an enormous dress that descends by a cable from the heavens (a ball-gown ex machina?) and daughters that grow more grotesque as they don more layers of gown. The sets, costumes and lighting all contribute to the aura of magic.

Conductor Mario Bernardi has forged just the right kind of balance for the French sonorities of the score. On opening night the vocal ensembles were not yet quite together, but the soloists sounded entirely comfortable.

WASHINGTON OPERA --

"Cendrillon." Remaining performances are on Friday, Monday and Thursday and a matinee on March 13.