Tristan und Isolde, Royal Opera House, London<br/>Werther, Grand Theatre, Leeds<br/>London Sinfonietta/John Adams, Queen Elizabeth Hall, London

Two images are in my mind as I start this review of Christof Loy’s Tristan und Isolde. The first is of Nina Stemme’s ecstatic Isolde, seated close by the slumped corpse of her lover yet utterly alone in the lovesick radiance of the Liebestod. The second is of a face blurred into hatred as its owner loudly booed Loy and his designers Johannes Leiacker and Olaf Winter only minutes later.

Had this gentleman been sitting on the left of the auditorium, where much of Loy’s extraordinary concentrate of text and gesture would have been obscured by a slanting, zincgrey wall, I could have understood his fury. But he was just behind me, stalls right, with an optimal view of what must be the most incendiary performance by a Wagnerian soprano for many decades. There can be little doubt that the hostility with which Loy’s production was greeted at the Royal Opera House on Tuesday was as much a reaction to his aesthetic as it was to compromised sightlines, yet performances such as Stemme’s do not occur in a vacuum. Loy’s approach has not softened since Lulu. There is no ship, in this Tristan, no castle, no cobwebbed fantasy of ancient Cornwall. Isolde’s transfiguration takes place on a plywood chair with metal legs, one of two that dress the front half of the set, while the back is laid with crystal and candelabras for King Marke’s wedding feast.

Monochrome is an inadequate term for Leiacker’s palette of silver, dovegrey, gunmetal, bone, bridal white, black and deepest indigo, or lighting that ranges from the softness of dusk to the brutal clarity of “deceitful day”. Menace and sweetness are here, from the tableaux of dinner-suited courtiers to the poignancy of Brangäne’s warnings, sung while Kurwenal idly strokes her arm, confident that their liaison is not transgressive.

Loy’s directing of the singers is dynamic. As Isolde and Tristan (Ben Heppner) fight for dominance in Act I, both veterans of a bitter war, first one then the other places their hands on that troublesome wall, leaning over their opponent. The love-potion is knocked back swiftly, roughly. Then time stops, body-language changes, and the lovers talk as though they had all the time in the world, laying a table for two, oblivious even when Melot (Richard Berkeley-Steele) draws up a chair to watch them. Though Heppner’s voice falters periodically, he is a poetic broken hero. John Tomlinson’s Marke conveys all the vulnerability of childless old age, while Sophie Koch and Michael Volle give spirit and fibre to Brangäne and Kurwenal. There is a lyrical Sailor from Ji-Min Park, while Stemme’s lustrous, direct, powerful sound is supple in fury, despair and rapture, almost playful in “O sink hernieder”.

In the pit, Antonio Pappano and the orchestra overcame a shaky Prelude in which the pulse was lost to Verdian limpidity. As accompanists, they excel, from the fluttering woodwind of the night, to the mordant blaze of offstage brass, the slow pangs of the opening of Act III and the intoxicating spasms of the Liebestod. For those audience members seated on the left, this is small compensation for the atrocious sightlines. For those on the right, it is close to Heaven.

Transfiguration is harder to achieve when you are responsible for six children yet Tom Cairns's Opera North production of Werther ends with Alice Coote's Charlotte scrambling for a gun to turn upon herself. History has been hard on the "Kinder, Küche, Kirche" heroine of Goethe's epistolatory novel and Massenet's Franco-Wagnerian masterpiece, and especially unforgiving of her refusal to follow Romantic protocol and die or at least succumb to insanity on Werther's suicide. "Charlotte, having seen his body/Borne before her on a shutter,/Like a well-conducted person,/Went on cutting bread and butter" quipped Thackeray in his verse satire "The Sorrows of Werther".

Well conducted as this Charlotte is (by Richard Farnes, in a pitch-perfect reading of this moth-soft, twilight score), Cairns and Coote emphasise the terrible burden of being good. Indeed, Coote's engagement with her dilemma – in the Air des lettres and Air des larmes, but also in the Claire de lune scene – is of such whole-body intensity that Paul Nilon's Werther becomes a warbling footnote to a one-woman psychodrama. As Sophie, Fflur Wyn offers a touching portrait of an adolescent hurled into the moral mess of adulthood, while Donald Maxwell (Magistrate) and Peter Savidge (Albert) convey the sadness of simple men whose dearest assumptions are dashed.

As with Tristan, the power-structure transcends the period. Nonetheless, Hildegard Bechtler and Amy Roberts's mid-1930s set and costume designs – all dirndls and trachtenhuts, in the heavily laundered pastels of Super-8 film – have a predictably unsettling effect. I spent much of Act II waiting for the first swastika to appear in Wetzlar, but even the fibreglass geese didn't goose-step.

The London Sinfonietta started its 09/10 season with a crisp, upbeat programme of American music under composer-conductor John Adams. In John Cage's Credo in US, samba, blues and boogie-woogie riffs for piano (John Constable), collide with a radio collage of shock-jocks, rappers and preachers recorded by Adams on the anniversary of 9/11. Paul Dresher's Concerto for Violin and Electro-Acoustic Band saw violinist Clio Gould serenaded by an electric guitar with Van Halen trills. (Schwing!)

Rhythmically, David Lang's Cheating, Lying, Stealing covered the same ground, moving from a syncopated 4/4 beat to 12/8 time. Adams's own Son of Chamber Symphony was an exuberant nod to its 1992 predecessor, all cartoon energy and virtuosic colour, with a gleaming oboe solo by Melinda Maxwell.

'Tristan und Isolde': ROH, London WC2 (020-7304 4000) to 18 Oct; 'Werther': Leeds Grand (0844 848 2706) to 24 Oct