I liked the stage direction “All hell breaks loose”. Perfect for a convent exorcism – the climactic event in this new opera, unveiled before a gourmet audience who would have probably preferred to be eating Mozart. But where was Hell exactly? I saw nuns in a polite flap, a little writhing, smeared blood: a tea party compared with the Exorcist films. Silviu Purcarete’s production of this imaginative but uneven opera by Peter Eötvös is troublingly cool, tasteful and careful.

To a degree, you can understand the caution. In a career of many operas, this was a big commission: Eötvös’s first for Glyndebourne; his first in English (well, mostly). And it’s based on no homely text but the 1994 novel Of Love and Other Demons by the Colombian master of magical realism, Gabriel GarcÍa Márquez. Music and drama must illustrate time shifting and collapsing, reality warping into the fantastic. How to deal, too, with the plot’s tricky core, the obsessive love of an 18th-century bishop’s librarian for a 12-year-old girl, the Marquis’s daughter, bitten by a dog, who acts as if she’s possessed?

Eötvös, a magpie and maverick figure, avoids the tut-tuts by giving the girl a vocal line so testing that only an adult could attempt the role. No matter how stratospheric the pitch or angular the leap, Allison Bell displays dizzying power as Sierva MarÍa, the little copper-haired heroine. The singing throughout is impressive, as is Nathan Gunn’s chest, revealed in two scenes during the librarian Delaura’s journey from bookworm to love’s slave. And no one could moan about Vladimir Jurowski and the London Philharmonic, tumbling with zest through Eötvös’s eclectic, quicksilver score, rich in ear-catching sounds, or the emotional tapestry of Helmut Stürmer’s lighting – so vital in colouring his rudimentary set and the ritualised staging.

Yet, by softening the dangerous liaison, Eötvös dampens the material’s fire. He’s not helped by his librettist, Kornél Hamvai. Action often arrives in simultaneous layers; languages crisscross. The libretto’s brief lines keep characters stunted, with few chances for modern opera’s version of an aria. Gunn’s lyric flight, resonant when it comes, is much delayed; Felicity Palmer’s combative Abbess is delayed even longer. As the Marquis’s housemaid, Marietta Simpson is luckier; that richly textured mezzo pleasurably warms up the early scenes. Robert Brubaker also raises the temperature in the Marquis’s dream aria, one of several stretches benefiting from Andu Dumitrescu’s discreet video projections.

Nothing is sustained: that’s the disappointment. Soaring scenes alternate with deserts. Instrumental finery flickers, then dies. Still, you’re never bored, and even that exorcism brings its reward – a haunting final scene coloured musically by the same celesta that started this erratic opera.

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