Il trovatore, Royal Opera House, London<br></br>Claron McFadden/London Sinfonietta, Queen Elizabeth Hall, London

It's got everything. And that's the problem

With such a wealth of daft operatic plots to choose from, you might wonder why the Marx Brothers took Verdi's lurid melodrama Il trovatore as the setting for their anarchic 1935 caper A Night at the Opera. Pop down to Covent Garden this week and you'll understand.

From a comedy writer's point of view, Il trovatore is the ur-opera. There's infanticide, suicide and fratricide. (Try saying that like Groucho.) There's a gypsy, a despot and a love triangle. There's nuns, and, in Elijah Moshinksy's half-serious, half-vacuous Royal Opera House production, there's guns. Big ones. But I suspect that Harpo, Chico and Groucho had a more subtle reason for using Il trovatore to satirize modern metropolitan – or Metropolitan – manners. I suspect they were plain tickled that "sophisticated" people pay good money to be un-sophisticated for a few hours and appear even more sophisticated for having done so. Had they chosen a work less greedy of the suspension of disbelief, less musically remarkable, and less illustrative of the 19th-century operatic cocktail – two measures inspiration, two measures idiocy, and as much hard cash as you can get your hands on – the joke would be less satisfying.

When Enrico Caruso quipped that all you need to make this opera work was "the four greatest singers in the world" he was not, in fact, joking. But ask any opera buff to fantasy-cast Il trovatore and you'll hear a different line-up. Covent Garden offers someone for everyone: Verónica Villarroel (Leonora) for Latin-traditionalists, Dmitri Hvorostovsky (Luna) for those who believe that the art of voice production has been lost to all countries outside of the former Soviet Union, Kundry-in-the-making Yvonne Naef (Azucena) for the more optimistic voice-spotter, and José Cura (Manrico) for the thousands of people who are more likely to have heard of him than the others. A lavish cast, then. But is it a cohesive one? No.

Despite this, despite the production's diffuse sense of location (Manet meets Goya meets Alma-Tadema), despite the exogenous rape scene, the lack of character development and the ubiquitous male dancers in tight leather breastplates, silk neckerchiefs, orange goggles and criss-cross thong-thingies over their thighs and buttocks, Moshinsky has done a reasonable job of staging the unstageable. The set pieces are impactful and his pacing echoes the plot's long game. Quite rightly, the love-triangle between Leonora, Manrico and Luna becomes incidental to Azucena's slow revenge. The emphasis is thus on maternity, fraternity and the devastation wrought in their name. But Moshinsky's partial success is largely down to the chorus (in magnificent form), the orchestra (ditto), and conductor Carlo Rizzi. Rizzi's reading is sharp, rich, uncompromising and dramatically acute. He teases phrases with a vocal nuance beyond most singers, and though his demands include some blistering tempi, I think he's right to make the score his priority. What a shame the stars don't.

As Leonora, Villarroel flounders. A steely yet mournful, classically Verdian voice is one thing. A steely yet mournful, classically Verdian voice that flips into phlegmy fluting at the top is another. Sure, the "top" in Verdi is dog-whistle high. More disturbing is her tendency to zone out. Note by long note you sense Villarroel monitoring her technical progress minutely: Ah... this is the F... now dimunuendo and... I'm moving to the G... ok, concentrate and... yes! Of course, no-one believes that the illusion of ease is anything but an illusion in arias like these, but this Leonora is emotionally absent. Which might be why Manrico displays more passion towards his (foster) mother, Azucena – though in Cura's unsubtle hands Italian filial devotion comes across as an Appalachian-style Oedipus complex.

Vocally it's fine: attractive, accurate, anatomically correct. Dramatically it's a mess. Gone is the bombastic eye-rolling and teeth-flashing of old. New-Cura now keeps moodily – and self-consciously – static, preferring to leave any movement to his mullet. Which could be why Hvorostovsky is yet more motionless. Who cares, was my first response, happily inclining to his elegant legato, cool inflections and burnished tone. He's lazy, was my second. Luna and Manrico seem more sulky than murderous during their multiple duels and it is Azucena – who Verdi, in revolt from the cult of high voices, believed to be the central character of Il trovatore – who does the hard dramatic, stylistic and vocal work. It is Azucena who juggles the roles of primary carer, professional plotter and queen bitch, holding everyone together all the while and not worrying about her increasingly frazzled appearance. But don't all good mothers?

Alas, Azucena is emphatically not a model mum – she incinerated her own son and stole someone else's – but Naef is a model opera singer. She creates a sympathetic character out of a double murderess while blending with the other singers and attending to the conductor. Her vocal production is technically superb – she knows when to merge and when to cut between registers – her musicianship excellent. Her performance is also the only one to embrace emotional complexity rather than run from it. For the rest of this starry, starry night? As Groucho once said, "I didn't like the play, but then I saw it under adverse conditions – the curtain was up."

The London Sinfonietta's first performance in Signs, Games and Messages, the György Kurtág festival, provided a seriously hostile obstacle course for the casual dabbler in contemporary music. Most of us were there for Kurtág's 1976 song-cycle Messages of the Late Miss R.V. Troussova – a work that eclipses Erwartung in its vitriolic and virtuosic exposition of romantic rejection – but goodness me we took a lot of stick before getting that carrot. Stockhausen's Kontra-Punkte – the musical equivalent of slapping someone because you can't think of a decent retort to five centuries of persuasive argument – followed by Kurtág's Mémoire de Laika – an electronic lament for the dog sent up in a sputnik – followed by an electro-acoustic hommage by the aptly named Nono? Before the interval? Returning for the second half was a very close call. To those braver or weaker – depending on your perspective – than me, I can only say that Messages was every bit as exhilarating, inventive and absorbing as the first half of the concert wasn't. A beautiful, brave and thrilling performance by Claron McFadden and an exemplary piece of ensemble work from the London Sinfonietta. Worth the torture? Yes. Just.

a.picard@independent.co.uk

'Il trovatore', Royal Opera House, London WC2 (020 7304 4000) to 14 May