If “semi-opera” sounds a half-and-half experience, then that’s what Purcell’s The Fairy Queen is: a freeish adaptation of Shakespeare’s fairy-land comedy A Midsummer Night’s Dream — possibly by Thomas Betterton, but nobody really knows — tricked out to epic lengths with a substantial score by England’s first great theatre composer. Glyndebourne’s spectacular new production is a first for the festival, and a rarity, in that Jonathan Kent’s staging gives words and music almost equal billing. We don’t get the whole caboodle — that would allegedly take between five and seven hours in the theatre — but it’s still a long haul. Not Tristanesque, as the conductor, William Christie, reassures us in a programme interview, but almost Lohengrin length.

Only Glyndebourne, I suspect, could muster the resources to put on an extended run of a staging like this, and even so, it needed co-producers to vouchsafe the wow factor of a true theatrical extra­vaganza. Purcell was writing for audiences addicted to what the fashionable French called “le merveilleux”: “miraculous” visual effects realised by elaborate baroque theatre machinery, including traps and flying apparatus.

Without attempting an authentic replica of a late-17th-century production, Kent and his inventive designer, Paul Brown, frame their thoroughly modern staging with the trappings of post-Restoration theatre. After the overture, the action of the play begins in a baroque drawing room with wall-cabinet displays of theatrical bric-a-brac. Theseus (William Gaunt) and Egeus (Terrence Hardiman) wear full Purcellian periwigs. As the lovers enter the magic wood, the walls disintegrate and Lysander (Oliver Kieran Jones) and Hermia (Susannah Wise) are stripped of their period finery by Nicole Farhi-clad fairies. (Sally Dexter’s Titania and Joseph Millson’s Oberon are darksome, alluring creatures with black angel-of-death wings.)

Kent’s staging of the play is full of witty detail — the smooth-skinned, tattooed Lysander provocatively pulls a hair out of the chest of his hirsute rival, Demetrius (Oliver Le Sueur) in the quarrel scene — and unashamedly contemporary in tone. The biggest laugh of the evening comes when Brian Pettifer’s deadpan Snug, as Lion in Pyramus and Thisbe, announces ‘And know that I, one Snug by name, a joiner am!”, and hands out his business card to the lovers — a stroke of blissful comic genius.

Yet Kent and Brown struggle to integrate Purcell’s masque interludes into the remains of Shakespeare’s play, unsurprisingly when The Fairy Queen calls for such unlikely episodes as a celebration of Oberon’s birthday, a scene for a drunken poet (sung more than adequately by Desmond Barritt, the garrulously boastful Welsh Bottom) and a golden Apollo on horseback, descending majestically in ultra-baroque style from the clouds. Kim Brandstrup’s ballet of bonking white bunnies goes a bit OTT, but it’s very funny.

Christie is a supremely devoted and stylish champion of Purcell, and the Orchestra of the Age of Enlightenment responds with verve to his zingy direction. Vocal delights are intermittent: Lucy Crowe dazzles with her every appearance, a young singer extravagantly blessed with look-at-me-and-listen charisma, and the bass-baritone Andrew Foster-Williams’s immaculate diction as Time and Hymen (a scruffy vicar brandishing a Sainsbury’s bag) is always a pleasure, but Carolyn Sampson’s thin-toned and textually opaque singing of the beautiful Plaint hardly justified her star billing above Crowe.

Grange Park and Garsington Opera — competitors for the Glyndebourne overspill market — go head to head with new pro­ductions of operas by Moravian composers: Janacek’s immortal Cunning Little Vixen (battily sung in Czech, despite having an entirely English-speaking cast) and Martinu’s Mirandolina, a justly neglected “masterpiece” if Martin Duncan’s colourful — cubism meets Italian ice-cream parlour — staging is anything to go by.

David Alden’s designer, Gideon Davey, moves Janacek’s Vixen from its forest setting into a pea-green-wallpapered room decorated with botanical illustrations. The American director — fresh from his ENO triumph with Peter Grimes — doesn’t really do charm or folk­siness, and his red-in-tooth-and-claw depiction of nature is only half of the story that Janacek tells. Only in the third act, as he underlines the loneliness of most of the human characters, the drabness of their existence, and the Forester’s optimism in the renewing power of nature (a fine Robert Poulton) does the staging match Janacek’s visionary music.

Ailish Tynan’s brittle soprano is good for the Vixen’s survival instinct, but she misses the sexual allure of the character by miles. André de Ridder and the English Chamber Orchestra make heavy weather of Janacek’s uplifting score.

Musical standards at Garsington are invariably higher, but even Martin André’s superb conducting of Martinu’s attractive, resourceful score can’t redeem Goldoni’s un­attractive characters. Even if you find misogyny funny, this yarn of a pulchritudinous innkeeper’s seduction of a dyed-in-the-wool woman-hater just for the hell of it seems painfully thin. She eventually dumps him for her manservant, and the duped, Malvolio-like Cavaliere di Ripafratta stomps off in a rage. Mirandolina is archly played and beautifully sung by Juanita Lascarro, a Garsington discovery making a welcome return, and Geoffrey Dolton works his silk stockings off, playing the Cavaliere as Kenneth Williams and Charles Hawtrey rolled into one, in Carry On Camping It Up style.

Covent Garden is mounting a comprehensively restudied revival of La Traviata as a showcase for the return of the American diva du jour, Renée Fleming. Not only has the Royal Opera’s music director, Antonio Pappano, deigned to conduct — his way with Verdi is suppler and more idiomatically Italianate than Georg Solti’s in 1994 — the original director, Richard Eyre, has returned to spruce the show up.

Fleming, who turned 50 this year, risks comparisons with Anna Netrebko’s youthfully glamorous star turn last season, but she surpasses all expectations. Her wasp waistline must be the envy of sopranos half her age, and she negotiates the hazardous vermicelli of Violetta’s Act I scene with rather more care for the small notes than Netrebko did.

If she doesn’t really sound Italianate, and her blonde Southern-belle wholesomeness looks a bit incongruous for a demi-monde 1860s Parisienne, she puts a lot of effort into getting the words across and her pearly middle-voice tones are still beautiful to hear. Fleming gets luxury support from Joseph Calleja’s elegantly phrased Alfredo and Thomas Hampson’s seamlessly sung Giorgio. Not to be missed if you can get a ticket.

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