It’s that time of year again for the dedicated summer opera-goer: champagne picnics, shivering in unseasonable cold wrapped up in rugs, and, for the braver sex, little black cocktail dresses. Or not, in the case of the American soprano Deborah Voigt, whose dismissal from the Royal Opera’s 2004 revival of Richard Strauss’s Ariadne on Naxos probably garnered her more publicity on either side of the Atlantic than anything she has actually sung. It will be remembered that Mme Voigt was deemed too big to appear in Christof Loy’s production of Ariadne, and, in particular, in the now notorious “little black cock-tail dress” designed by Herbert Murauer for Petra Lang in 2002.

Now, after much-publicised stomach-clamping surgery, a less ample Voigt has been readmitted to the Covent Garden fold, and the RO has done what it could easily have done before: designed her a new frock. Even if the new, slimmed-down Voigt is no sylph, she looks handsome and carries herself with the hauteur of a visiting diva, her travelling moral high ground neatly packed in her carry-on suitcase when she makes her entrance into the lift of the two-level Grand Hotel, Murauer’s spectacular set for Strauss’s Prologue “in the house of the richest man in Vienna”.

Voigt has clocked up column inches like air miles for her dismissal, dramatic weight loss and comeback — too many, perhaps. Her antics on a recent YouTube posting, in which she does a would-be comic skit with an animated cocktail dress, have played well to opera-lovers in America, who have greedily swallowed the line that l’affaire Voigt is a dastardly British plot against American singers in particular and fat people in general. But to the rest of the world, it must now look like she and her PRs are milking a grudge match to its limits. Voigt needs to move on: she looks great, moves with considerably more freedom than of yore and still sings a pretty good Ariadne.

Perhaps her voice has lost some of its former tonal “fatness” with the stones she has shed, and she had a little vocal accident as she ascended to the stratosphere at the climax of her first aria in the opera proper. She quickly recovered her equilibrium, however, and only the occasional ill-tuned floated note suggested that her technique has not survived unscathed. Hardly the most compelling of actresses, she is self-deprecatingly witty in the diva tantrums of the Prologue and presents a sympathetic character as the abandoned Ariadne, longing for death, in the candle-lit Viennese drawing room that does duty for Naxos in Loy’s staging. Her return was not perhaps the thunderous triumph she might have wished for, but she was warmly received.

Loy’s production is still one of the smartest shows in the RO’s repertoire, even if the deliberate dislocation between the Prologue and the opera-within-an-opera remains problematic and baffling. The newly knighted Mark Elder conducts with a sure grasp of Ariadne’s hybrid nature: a rococo, Mozartian pastiche that morphs ecstatically into a Tristanesque world of darkness, death and transfiguration. Voigt was joined by her compatriot Robert Dean Smith, the most vocally confident Bacchus at Covent Garden since the late James King, who made light work of Strauss’s arduous, tenor-baiting notes.

Earlier in the opera, Gillian Keith, got up to look like Twiggy as if dressed by Mary Quant, negotiated the coloratura terrors of Zerbinetta’s grand scena nimbly and coquettishly, though she had struggled to make herself heard in the Prologue, which was properly dominated by Kristine Jepson’s impassioned Composer.

Strauss’s little masterpiece about the workings of the theatre and the relationship of the artist with patron tends to bring out the best in opera companies.

Garsington Opera brought it off splendidly last year, but this year the Oxfordshire garden enterprise fell flat on its face with what its general director called the first instalment of a “Vivaldi adventure”. If the Venetian composer’s limp L’incoronazione di Dario is typical, this is an endeavour doomed to failure. David Freeman, usually a cutting-edge director, struggled in vain to make big theatrical statements of Vivaldi’s string of uneven arias, and settled, quite understandably, on a send-up of the genre, devising camp routines in a misguided attempt to conceal the vocal shortcomings of most of the cast. Paul Nilon made a brave fist of the titular Dario, while sounding as if he wished he were singing Puccini, and the young and buxom Sophie Bevan introduced a soprano of immense promise in the secondary role of Alinda. Of the principals, only Renata Pokupic (Statira) gave an inkling of what an exciting performance of a Vivaldi opera might be.

This year, it was the turn of Grange Park Opera — a Garsington spin-off in rural Hampshire — to trump its alma mater with an astonishingly successful staging of Puccini’s demanding Wild West opera, The Girl of the Golden West. Stephen Medcalf and his resourceful designer, Francis O’Connor, shoehorned a piece premiered at New York’s 4,000-seat Golden Horseshoe in 1910 into GPO’s eight times more intimate space, to quite brilliant effect. Their production pays homage to the Royal Opera’s iconic 1977 staging, to be revived later this year, but manages to make Puccini’s original spaghetti western look fresh-minted.

The serviceable voices of Cynthia Makris, as the gun-toting, poker-game-cheating heroine who has never been kissed, John Hudson, a very English-sounding tenor whom nobody is likely to mistake for a dashing Mexican bandit rejoicing in the alias of Dick Johnson, and Olafur Sigurdarson, as the jealous Sheriff, hurled out big, sometimes exciting, but not very subtle noises into the tiny auditorium. Best of all were Rory Macdonald’s superb conducting of Puccini’s most demanding score and the fine playing of the English Chamber Orchestra. Macdonald is an opera conductor to watch, and destined for greater things.

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