La verit&#224; in cimento, Garsington Opera, Oxfordshire<br/>Le Cercle de l'Harmonie / Les El&#233;ments, Barbican, London<br/>A Salute to Percy Grainger, City of London Festival, London

Outstanding singing and dynamic conducting eclipse the visual effects of a rarely staged opera

Where Handel feeds on psychological ambiguity, Vivaldi strikes a pose.

Written for the Teatro Sant' Angelo in 1720, with a modishly exotic setting for its convoluted plot of past and present love triangles, La verità in cimento ("Truth on trial") is Venetian opera at its most baroque: a series of heroic attitudes betokening love, shame, triumph or despair, each as vivid as the heatwaves and thunderstorms of his famous set of violin concertos, The Four Seasons.

David Freeman's Garsington Opera staging of La verità transposes the court of Sultan Mamud (Paul Nilon) to a Victorian glasshouse peopled by extras from a 1980s pop video. Duncan Hayler's wintry, monochrome set is dominated by a white papier mâché tree. Swapped at birth, the Sultan's bizarrely coiffed sons Zelim (James Laing) and Melindo (Yaniv d'Or) vie for the hand of Rosane (Ida Falk Winland). Meanwhile their mothers, one a vampish scarlet lady (Diana Montague), the other the frumpish Sultana (Jean Rigby), slug it out like Joan Crawford and Bette Davis.

On stage, languid artifice is all. In the pit, Laurence Cummings and Garsington's versatile modern-instruments orchestra present a far warmer reading of Vivaldi's attitudes. Here is the wit, the drama, the drive: in the animated ostinato figures for cello and bassoon, the limpid violin and recorder solos, the pomp of trumpets, horns and oboes, the percussive bite of harpsichord and guitar, the sweet balm of the harp. Here too is character: in the shy lilt of Laing's "Tu m'offendi", in the agitated harmonies of Nilon's Act II peroration, in Montague's nagging "Lagrimette alle pupille". The ensemble writing is startlingly inventive, the arias scintillating. With outstanding vocal performances from Montague and Winland, and dynamic conducting from Cummings, Vivaldi's opera demands to be heard if not, in this chilly production, seen.

Le Cercle de l'Harmonie and Les Eléments made their UK debut on Tuesday in the Barbican's midsummer Mozart series. Under Jérémie Rhorer, their performances of the Vespers of the Confessor and the Mass in C minor were meticulously nuanced, with muscular sforzandi and crisp consonants. Never recklessly fast, Rhorer stretched the pulse of the Laudate Dominum to a point just shy of incoherence, though Sally Matthews's dark vowels and even vibrato made something wonderful out of its timelessness. As severe of demeanour as Andy Murray, as glamorous as a movie star, the British soprano engaged in an exhilarating rally of high Bs and As with mezzo-soprano Ann Hallenberg in the Domine Deus, and delivered a flawless Et incarnatus est to Le Cercle's equally flawless flute, oboe and bassoon soloists.

The City of London Festival's special gift has always been its interiors. Every summer, buildings you cannot otherwise enter are thrown open to music lovers. Last Sunday, however, the focus was outdoors, as nine pianists from the Centre for Young Musicians and Guildhall School of Music took a hardy group of listeners on a lunchtime walk from the Millennium Bridge to St Paul's churchyard and Paternoster Square. Directed by Helen Reid, with recorder player and singer Jill Kemp as pied piper, this was a tour of the festival's 15 street pianos and A Salute to Percy Grainger, the most famous of the Antipodean composers to be featured this year. At every stop, tourists watched and small children danced as Grainger's semi-serious arrangements of "Shepherd's Hey", "Hermund the Evil", "Let's Dance Gay in the Green Meadow" and "English Country Gardens" bounced off the marble facades of the Square Mile with nary a hollyhock in sight. Pure giddy fun for a sunny day.

'La verità in cimento' (01865 361545) ends tomorrow

Next Week:

Housework? What housework? Anna Picard goes to the ball as Laurent Pelly's production of Cendrillon opens at the Royal Opera House

Classical Choice

A double-dose of Steve Reich at the Cheltenham Festival today with Electric Counterpoint, Six Marimbas Counterpoint and Vermont Counterpoint performed by Kuniko Kato at the Parabola Arts Centre and Drumming at the Town Hall. In London, Liam Steel's Opera Holland Park production of The Marriage of Figaro opens tomorrow.