Scored for soloists, mixed chorus, children’s chorus and chamber ensemble, Iannis Xenakis’ music for Oresteia has been cited as “ruggedly dissonant” since its 1987 première in Sicily. Here in Basel, under conductor Franck Ollu's baton, its harsh, squealing chords, sliding sitar-like cello lines and whining wind instruments nevertheless reflect the tensions, horrors and misfits that are featured in Calixto Bieito’s production.

A wooden-planked stage is empty save three platforms, one each for the chamber players and percussion, another for a drummer on a separate perch. On a high screen to start, a loop video shows an almost-naked woman stretched out face down in a bathtub who is being hosed down uninterruptedly with water. No forewarning, and the clip changes to a thick forest, a small girl being physically abused by an adult man. While the same video images reappear at the end of the opera, but it’s nebulous soft-edged shapes – mood landscapes, as it were – that are the usual backdrop for the 90-minute piece.

The Oresteia revolves around revenge and bloodshed, and two choruses of some 60 singers convey much of the drama. Their vocals, marked by highly stylized, protean language in chanting rhythms to begin, become looser, and more ritualistic as the evening wears on. The choir’s command of its fairly “un-vocal” score was commendable, and under Henryk Polus’ direction, it made a thick, contiguous texture of visuals and curious sounds throughout.

Costuming was somewhat more pedestrian. The adult choristers appear in the frumpy styles of the 1950s; the children’s chorus – aligned to the glimmer of hope that the “democratic” end portends – make their much briefer appearance in prim school uniforms of grey gabardine. The principal singers are all more or less in the constant throes of cross-dressing, undressing, or not dressing at all.

Basel has something of a reputation for this kind of exposure, but inasmuch as infidelity and abuse of trust are the triggers that set the whole drama in motion, being scantily clad seems justified here. Granted, it was somewhat distracting to see Myriam Schröder sing her superb Clytemnestra in skivvies alone, yet undoubtedly her mastery of the treacherous vocal score was as attention-getting as her flanks of flesh.

As Cassandra/Goddess Athena, Holger Falk gave an astonishing performance. His tenor was stretched to the limits of human possibility, and he skated through the frenetic intervals and Herculean demands on his range as if all of it were easy. His encounter with the modern triangular version of the Aeolian harp – here in the multiple roles of instrument, conversational partner, and vulva – was a showstopping insight into the claims of honour, identity, and needy sexuality.

Simon Zagermann’s Agamemnon, too, gave a stunning performance around the tragedy of the “human slaughterhouse washed in blood,” and I found his character the most earthbound of the bunch. As his daughter Electra, the wistful Lisa Stiegler had some haunting stage directions: watching her father rape her mother, she bent towards them, salivating and repeatedly rolling out her tongue. As Aegisthus, Steffen Höld played both throne usurper and Clytemnestra’s lover with a confident hold. After his return from the dead, he also took the unenviable role of a PR man; moving among the audience’s seats to drum up applause for Athena’s final decree of justice.

Towards the end of the opera, the stage – like Agamemnon’s noble house – is torn up before our eyes. We watch as Clytemnestra smothers her husband, a glob of blood passing her lips as she finishes the gruesome job. The choir emerges on hands and knees like roaches  to stand, for the last third of the opera, facing the audience frontally, much like the figures from “The Night of the Living Dead.” Unable to cope with the “horrors, terrors, and agonies” he knows he must revenge, Orestes (Michael Wächter) undergoes a tortuous battle with his conscience. It was high drama, certainly, yet his writhing and trembling became somewhat pat and more than my patience could manage. Worse, a strong raking light bore down on the audience in the second half, as if we were the guilty deserving interrogation.

While his mother pleads he is “the snake I bore and nourished” and begs her life be spared, Orestes’ strangling her is graphic or gory, befitting his conscience, but seeming to take forever. Afterwards, he systematically unhinges and stacks nine or ten planks of the stage, and a huge crack opens up behind him, making a real case for how “things fall apart.” It’s only the goddess Athena, (again Holger Falk) who sets the record straight. She/he insists on an end to the violence and revenge, asking her countrymen to choose justice over entropy, and “let men give joy for joy.” Athena’s final underscoring the need for democracy is a compelling argument, one which possibly renders parts of the production even more poignant today.