A delightful collision of Henry Purcell's rarified florid music; William Shakespeare's comedy "A Midsummer Night's Dream;" and classic dance is taking place this week, in the Howard Gilman Opera House at Brooklyn Academy of Music (BAM), in Les Arts Florissants' production of the 'semi-opera' "The Fairy Queen" (1692), and the result is a most fascinating, if lengthy, entertainment. Music Director William Christie presides over this "Fairy Queen," a co-production of England's Glyndebourne Festival Opera, Paris' Opéra Comique, Théâtre de Caen, and BAM, which had its American premiere here on March 23. Fourteen Arts Florissants solo singers, sharing more than 20 roles, and the Arts Florissants Choir and Orchestra execute Purcell's incidental music for the play, and more, immaculately. A troupe of 16 actors performs most of Shakespeare's play. And a corps of eight, dancing choreography by Kim Brandstrup, helps tell the tale. The over-the-top production is directed by Jonathan Kent, with sets and costumes by Paul Brown, and lighting by Mark Henderson.

After the overture, we meet the quartet of young Athenian lovers-Alice Haig as Hermia, Nicholas Shaw as Lysander, Gwilym Lee as Demetrius, and Joanna Herbert as Helena-and Robert East as Egeus, Hermia's father, who lay out the basic conflict before William Gaunt, as Theseus, Duke of Athens, who is to act as judge. The rustic players first appear, cloths, squeegees, sprays, and vacuum in hand, to clean this sumptuous room in Theseus' palace, and start making plans for the play-within-the-play, "Pyramus and Thisbe," that they will enact. Desmond Barrit immediately establishes himself as a scene-stealing Bottom and even gets to sing some of Purcell's music, the part for 'the drunken poet'-"Fi-fi-fi-fill up the bowl"-with the black-clad, black-winged fairies, who attend Amanda Harris, as Titania, the Fairy Queen, and Finbar Lynch, as Oberon, the Fairy King. Roger Sloman, tenor Robert Burt-responsible for more than one drag role, Paul McCleary, Brian Pettifer, and Jack Chissick play Barrit's comrades. The fairies emerge from below the stage, are lowered from above, or enter through Theseus' huge curio cabinets. Jotham Annan is the lithe Puck, who does Oberon's bidding. Vanya Lawson and Coco Monroe alternate as the Indian Boy, in Titania's care, but coveted by Oberon, who snickers nastily when Titania says that the boy's mother, "a votress of my Order," died in childbirth.

A solo tenor, and then a trio of male fairies hail the birds, two male dancers-"Come all ye songsters of the sky," "May the God of Wit Inspire," and "Join Your Warbling Voices"-and are put out when two more trios echo them. Taking up the remainder of Act Two are Titania and her train's preparations for her sleep. A giant spider is lowered from above and fairies wrap their Queen in strands from its web, making a cocoon in which she will spend night. As the sun sets, represented by a stylized disc, Night (soprano Emmanuelle de Negri), Mystery (soprano Claire Debono), Secrecy (tenor Ed Lyon) and, finally, Sleep (sonorous bass-baritone Andrew Foster-Williams) lull Titania and welcome her into their realm.

Thanks to the juice of a rare, magic flower, Puck, instructed by Oberon, mistakenly makes Lysander fall for Helena, instead of Hermia, and mischievously changes frumpy Bottom into a jackass, during the rustics' rehearsal, frightening them off, and Titania falls for him. Entertainment for Titania and her asinine swain occupies the rest of Act Three and one highlight depicts the pastoral courtship of Coridon (Foster-Williams) and Mopsa, the shepherdess (Burt), who, coyly resisting, puts Coridon in his place before hitting the hay-stack with him. Soon he deserts her for a childlike nymph (Debono), with a large lollipop, singing, "When I have often heard young maids complaining." Easter comes early to BAM, as a troupe of bawdy bunnies, doing what bunnies do best, perform the Dance for the Haymakers, song "A Thousand, Thousand Ways," and hornpipe that concludes the act.

After intermission, Oberon and Titania reconcile and Act Four concerns the lavish celebration of the Fairy King's birthday, after Night (de Negri) "is chased away," with a pageant of the Seasons, courtesy of gold-clad sun god Phoebus (bass Andrew Davies), who is lowered in, seated on his magnificent golden-winged horse, to end the "cruel long winter." Debono is "the ever grateful Spring;" countertenor Sean Clayton, wearing a red, yellow and orange skirt and twirling a parasol, is the travesti "Summer, sprightly, gay,/smiling, wanton, fresh and fair;" countertenor David Webb is Autumn, a scarecrow in ballooning pantaloons, overseeing "many coloured fields/and loaded trees;" and Foster-Williams is hoary Winter, stiff and white-bearded, who "comes slowly, pale, meagre and old."

In Act Five, the dénouement, the Athenian lovers are paired up as they're meant to be, and an equestrian Theseus urges Egeus to accept the outcome, Bottom awakens, shorn of his ass ears, beneath the hind end of Theseus' mount, and the weddings of Hermia to Lysander and Helena to Demetrius are blessed and celebrated. Juno (soprano Lucy Crowe), suspended mid-air, honors the couples with an epithalamium, "Thrice happy lovers;" de Negri sings a melancholy plaint, "O, O let me, let me weep," for balance? to ward off the evil eye?; Adam (Lyon) and Eve (soprano Helen Jane Howells), in their fig leaves, sing their solos, "Thus, thus the gloomy world," and "Thus happy and free," eat the forbidden fruit, become shameless flirts and, alas, learn shame; the female fairies trade in their wings for 1950s fashions, with the men, still wearing wings, in tuxedos, and grumpy Hymen (Foster-Williams) is summoned-"Sure the dull god of marriage does not hear"-and, though disenchanted by "false flames, love's meteors," "where hardly love outlives the wedding night," dons clerical collar and unites the true lovers, relieved that, "My torch indeed will from such brightness shine." Finally, the rustics perform their "tedious brief" play of "tragical mirth," in tatty finery, introduced, with due pomp and ceremony, by McCleary's Quince, and every bit the joy it should be, with Barrit's Bottom as Pyramus, the knight in not terribly shining armor; Burt's Flute, in slutty drag as his love, Thisbe; and the slow ones, Chissick's Snout as the Wall that separates the lovers; Pettifer's Snug as the lion that frightens Thisbe and claws her mantle, making Pyramus believe her dead; and Sloman's Starveling as the moon that lights the lovers' meetings, completing the cast.

There are, at this writing, three more opportunities to experience Les Arts Florissants' "Fairy Queen"-on March 25, 26 and 27, at 7:30 p.m., with Jonathan Cohen replacing Christie in the pit for the final performance. For tickets at $35, 65, 105 or 150, visit www.BAM.org, telephone BAM Ticket Services at 718/636-4100; or come to the box office at 30 Lafayette Avenue, off Flatbush Avenue.