DON'T GO to the Washington Opera's production of "King Arthur" expecting a scholarly recreation of the 17th-century dramatic and musical world of John Dryden and Henry Purcell, and certainly don't go expecting grand opera. In fact, it is probably best to go (if you can wrangle tickets to this sold-out run) with no preconceptions whatever. Director Colin Graham has cut and pasted and otherwise transformed what was a rambling 17th-century masque into a show more appropriate to the contemporary stage. In doing so, he has defined a new opera idiom.

Arthur, King of Britain, struggles against demonic magic to rescue his queen, the blind Emmeline, who has been kidnapped by Oswald, King of Saxony. This is the essence of the plot. But the first thing you notice is that both Arthur and Oswald are young guys in jeans and motorcycle jackets, and that the trio of nasties who help Oswald in his nefarious schemes look and act an awful lot like street punks. Emmeline, however, and Merlin, Grimbald (a wonderful horned devilish spirit) and Philidel (a kind of puckish good fairy) are clearly and comfortably denizens of the land of make-believe. That there doesn't seem to be any incongruity in all this is testimony to Graham's genius.

The Washington Opera has done what it is best at: It has gathered together a large cast of relatively unknown young singers who can handle their assignments with a fine sense of vocal and dramatic style and energy, and has coached them into a coherent team. Kurt Ollmann and Carl Halvorson are attractive as the contending Arthur and Oswald, and Sylvia McNair is an appealing Emmeline (but only through Sunday, after which Amy Burton assumes the role). Kimm Julian, a larger-than-life Merlin, combats the sorcery of Gordon Holleman's coniving Guillamar with flair and authority.

Kurt Link is an inspired Grimbald who plies his evil in the guise of a dirty old lady, a glorious snow storm and a grotesque earth spirit, and Elisabeth Comeaux moves with such grace and compelling good humor as Philidel that it is almost a surprise when she breaks out in delightful song. The smaller roles are equally well-served and two on-stage trumpeters and an outstanding chorus round out an unusually well-balanced company.

Graham's set is a post-and-lintel gateway about which, from time to time, supers hold up stylized trees or billowy cloth "waves." There are occasional flashes of smoke and flame and a delicious dragon assists Merlin in some of his exploits, but, in general, Graham has shown admirable restraint in the use of gimmicks.

Under Stephen Lord's conducting, the Opera Orchestra and the ensemble in general sounds elegant and absolutely secure, and the pomp and lilt that makes Purcell's music such a delight is delivered with a stylish joy that makes this production a rare treat.

THE WASHINGTON OPERA -- Purcell's "King Arthur." Continues Friday, Sunday (matinee), Jan. 18, 21, 27 (matinee), 29, 31 and Feb. 2 at the Kennedy Center Eisenhower Theater. Performances are sold out by subscription. Standing-room tickets are $10 and go on sale at 10 (noon for matinees) at the Kennedy Center ticket office. Returned tickets go on sale at the center's concierge desk one hour before performance. Call the Washington Opera box office at 202/416-7800.