Kafka's Trial, Operaen, Copenhagen <br/> Gustav Mahler Jugendorchestra, Barbican Hall, London

Like Welsh National Opera, the Royal Danish Opera company christened its new waterside home with a crowd-pleasing burst of core-repertoire Verdi. But the company's first event of real significance came six weeks later when the world premiere of Poul Ruders' Proces Kafka, or Kafka's Trial, opened in Copenhagen's breathtaking maple, concrete and glass Operaen.

Like Welsh National Opera, the Royal Danish Opera company christened its new waterside home with a crowd-pleasing burst of core-repertoire Verdi. But the company's first event of real significance came six weeks later when the world premiere of Poul Ruders' Proces Kafka, or Kafka's Trial, opened in Copenhagen's breathtaking maple, concrete and glass Operaen.

Europe's answer to John Adams, Ruders has absorbed the shock of modernism and the severity of minimalism and blended them with bravura seriousness. Stylistically, he is eclectic; capturing the atavistic kick of popular music, the harmonic translucence of Boulez, the brutal rhythms of Bartok, the blood-red colours of Janacek, and the sleek spaciousness of Sibelius. Yet his music remains his own; its identifying feature being an otherwordly aural smudge as he slips between planes of sound. (Picture the blur of colour at the edge of a Rothko rectangle and you've got it.) Among contemporary composers, he is one of a tiny handful writing operas of international appeal. A Handmaid's Tale (2000), his skilful adaptation of Margaret Atwood's dystopia, was rapturously received everywhere but in Britain.

For their second collaboration, Ruders and his librettist Paul Bentley have revisited the dual-reality they essayed in A Handmaid's Tale, where the stories of Offred's life in The Commander's House and her life in The Time Before unfold in parallel and the central role is split into two. In Kafka's Trial, Bentley has inverted and extended this device: exploring the parallels between Kafka's affairs with frigid Felice Bauer and libidinous Greta Bloch and the triangular relationship between Josef K and Fraulein Bürstner and Fraulein Montag; using the same trio of singers for all six roles; combining lines from Kafka's letters to Bauer and Bloch with lines from The Trial; shadowing the tenor who takes both K-roles (Johnny van Hal) with silent doubles, and turning a bleak novel of alienation into what might best be described as a Surrealist sex comedy. It's a nice idea on paper. It has some great lines, some eye-smarting slapstick, a vast amount of slap-and-tickle, and some wonderful music. But as a dramatic narrative it is terribly stilted.

Bentley and Ruders have concentrated too heavily on their reading of Franz Kafka; a man who went to great lengths to obfuscate his feelings on the rare occasions that they were not chronically ambivalent. That his disastrous double-affair with Bauer and Bloch inspired The Trial is widely acknowledged. (Kafka refered to his showdown with Bauer's family as a Gerichtshof, or court of justice.) But portraying the novel as a Freudian nightmare in which every character is a manifestation of the dreamer weakens its impact and forces Ruders to abandon his most promising ideas before they can flourish. Set pieces for the court aside, the most developed writing is found in the biographical sections.

The Prelude, entirely biographical, is magnificently detailed: Kafka's guilt-ridden references to his father are decorated with the melismas of the Synagogue and unfurled over thin, elevated chords, while his dysfunctional romance with Bauer reaches a climax to the shriek of klezmer clarinets and swirling strings that greet their official engagement. But having pumped up the black humour in Kafka's own sexual, creative and bureaucratic dilemmas, a frantic game of Snap! between novel and biography ensues. The pathos of both narratives is diminished, their conclusion lame. And Francisco Negrin's self-conciously spectacular production doesn't disguise this. Keen to prove that he has read around his subject, Negrin has Lawyer Huld (Bo Anker Hansen) appear as a beetle, the Interrogator (Johan Reuter) as an eagle, and Gert Henning-Jensen's Inspector as a slit-walking K. Meanwhile, in their Bürstner and Montag roles, Gisela Stille (doubling as Bauer) and Marianne Rorholm (also Bloch and Leni) are pornographically plump invalids pushed about on chaises longues. Paul Steinberg's designs here are strongly reminiscent of the Prinzhorn Collection of "degenerate" art from Europe's psychiatric hospitals; a nice touch.

In terms of its musical execution, if not that of Josef K, Kafka's Trial is a triumph. Conductor Thomas Sondergard's fluency in Ruders' exacting argot is absolute, his orchestra radiant in the enviable Operaen acoustics. Among the cast, van Hal wrestles manfully with a demanding vocal range. Stars of the show, however, are Rorholm (who created the role of Offred) and Hanne Fischer (Offred in The Time Before), whose brief roles as the Washerwoman and the Hunchback have a warmth and humour significantly lacking elsewhere. Somewhere in Kafka's Trial there is a great score to be found, but Ruders' unique operatic talent has been thwarted by an unwieldy concept.

So to a brief appreciation of the Gustav Mahler Jugendorchester, whose beautifully responsive performance of Mahler's Rückert Lieder with a snuffly Simon Keenlyside showed that even the largest of orchestras can accompany an ailing singer with the delicacy of a pianist. In the short-breathed exhortations of Des Antonius von Padua Fischpredigt I wondered whether Keenlyside's cold was too compromising, but I would not have missed his account of Ich bin der Welt abhanden gekommen for all the Lemsip in Leamington Spa. Conductor Franz Welser-Möst's distinctive lightness of touch was clearly inspiring to his pan-European band of Wunderkinder. Basses, horns, bassoons and upper strings inclined to the rhythm like a chamber ensemble, lending sprung intimacy to Strauss's rarely performed (rather silly) Alpine Symphony. Their solos were exquisite.

'Kafka's Trial': Operaen, Copenhagen (00 45 3369 6969/ www.kgl-teater.dk), to 13 April

a.picard@independent.co.uk