21st century opera is a broad church. There aren’t many of us, I suppose, who are intimately familiar with the biographical accounts of the lives of 13th century troubadours, popular at the time in Spain and south west France. But Martin Crimp and George Benjamin, librettist and composer of Written on skin, aren’t exactly run of the mill people.

[Spoiler alert] The source for Written on skin is the tale of the troubadour Guillem de Cabestaing and his adulterous affair with the wife of the nobleman in whose house he was employed. On discovering the affair, the husband cut out Guillem’s heart, cooked it and served it to his wife, in pepper sauce. It’s an extreme story, and Crimp and Benjamin have fashioned it into an extreme opera, changing the troubadour to an illuminator to better distinguish the character (in an opera, everyone sings, so a troubadour isn’t exactly distinctive). The title refers to mediaeval manuscripts being written on parchment, a material made from animal hide.

With almost all of the opera being sung by three characters, it is compact in format. At 95 minutes, it's also short, and the highest pitch of dramatic intensity is maintained throughout. As the action winds from the initial hubris of the brutal but sexually ambivalent husband through our discovery of the wife’s own sexuality and on to the grisly climax and its surprising aftermath, the drama is constantly gripping.

Benjamin’s score shines in his contrapuntal vocal writing. The bulk of the opera is in duets between pairs of the main characters, in which Benjamin sinuously interweaves the lines of the different voice types (soprano, counter-tenor and bass), creating passages which are beautiful and poignant as well as dramatic. All three main singers were superb, with clear diction and excellent projection of their characters. Barbara Hannigan’s voice was extraordinarily flexible whether in sweetness or steel; Christopher Purves was powerful, authoritative and frightening; Bejun Mehta’s countertenor was both passionate and other-worldly.

The orchestral score is varied in timbre, with a wide variety of percussion instruments and glass harmonica in addition to conventional orchestral forces. It is less varied in mood, which is predominantly dark, brooding and tense. On a small number of occasions, the tension explodes into violence: these moments were impressive and virtuosic, and I wished for more of them. Outside these climaxes, Benjamin draws from such a large palette of sounds, tonalities and atonalities that my ears, attuned to more formal compositions, found it difficult to discern form or progression.

Crimp’s libretto is taut, straightforward and mostly prosaic. A notable stylistic element is that the characters frequently use the third person to describe what they themselves are doing, creating a slightly spooky distance between performer and role. There were moments of entrancing poetry: a metaphor sticks in my mind of the lover reaching into a tree and bending a willingly yielding branch downwards so that he can pluck the fruit of the woman’s love. But as with Benjamin’s moments of extreme music, I wished for more of these moments of extreme poetry.

More frequently, the main story is seeded with references to the present day. This goes with a framing story in which seven “contemporary angels” (three sung, four mimed) take part in proceedings, bringing the humans dreams or tormenting them with callous divine power. In Katie Mitchell’s split-level staging, the main action takes a place in a sub-stage (colours: drab, lighting: subdued, decor: plain, maybe mediaeval) flanked by present-day rooms (colours: white, lighting: bright, decor: office). The smartly clothed angels also dress the mediaeval characters and usher them on and off stage; throughout the action, we see them in profile, pacing slowly around their areas.

This aspect of the opera annoyed me: I doubt I would have understood it at all without careful reading of the programme before the show. Unlike the enormous power being generated by the ancient story, the dialogue in these present day elements seemed scattered and incoherent; when, in the mediaeval space, the Boy sang that in future, his woodland will be riven by an eight lane motorway, I found it embarrassingly trite. I understand that Benjamin, Crimp and Mitchell strongly desired “to move deftly between the past and the present”, as Kasper Holten’s programme note describes it, but for me, that movement was clumsy rather than deft.

But while Written on skin has no shortage of imperfections, they are relatively insignificant when set against its qualities: this is an evening of immense drama where the music and singing give force to an extraordinarily dark tale, with some amazing vocal writing performed by three excellent singers. It’s a work that totally grabs your attention and shows how varied, interesting and powerful modern opera can be.