Opera: The Wildman

Nicola LeFanu's new opera The Wildman, premiered on Friday to open this year's Aldeburgh Festival, might have been called The Creature from the Black Lagoon II, for its story has at its heart the elemental directness of the best B-movies. Kevin Crossley-Holland's libretto derives from 12th-century Suffolk legend: out trawling, the fishermen of Orford capture a creature, half man and half beast, who terrifies them by his hairy strangeness and lack of human speech. The townsfolk lock him away; but the local constable's wife and children learn to respond to his strangeness, and he to them. When he finally recovers his speech, he tells his story, then swims back out to sea, leaving Orford to ponder how he has changed the town.

It's a simple morality tale, rather blurred by incidental details deriving from the decision to set it in the 12th century. Costumes might have been borrowed from a 1950s children's TV serial; and several plot strands lead nowhere, stretching the work out over two hours when, like the best B- movies, it should last 84 minutes. Nor is the drama aided by such Z-movie dialogue as "You dirty Breton!" - hurled at a scheming villain from, you guessed it, Brittany.

There is much beauty in LeFanu's orchestral writing, played by 11 members of the Britten Sinfonia, skilfully handled by Nicholas Cleobury. The gentle, undulating instrumental surfaces are occasionally broken by a solo instrument, with some lovely oboe, or beguiling bowed percussion for the Wildman's more waterbound moments. Yet, perhaps because of the libretto's excess baggage, much of the vocal writing fails to reach operatic temperature, simmering only as a kind of attenuated recitative. Most of the eight singers double roles, changing costumes in plain sight: admirable economy, but it already suggests a kind of undifferentiated vocal drama.

But whenever things threaten to disappear beneath the waves of gentility, Gwion Thomas's Wildman powers across the stage, slithering and sliding, howling and gibbering with terrifying ferocity. Unsurprisingly, his nakedness is masked by a thoroughly 20th-century pair of swimming trunks, yet he manages to generate a surging intensity, even while Graham Devlin's staging strives for inoffensive naturalism.

Designed to tour, Marise Rose and Ali Allen's set is flexible and mobile, beginning as a toytown castle but easily accommodating both interiors and exteriors. Ben Ormerod's lighting is equally adept at changing the mood in a moment, yet such precise technical inventiveness only underlines the lack of precision in the drama itself.

On Saturday, Oliver Knussen conducted the UK premiere of Magnus Lindberg's Aura. The BBC Symphony Orchestra can rarely have sounded so inspired. Lindberg's fabulously rich score works almost like a piece of weaving, its lines threading back and forth across the stage, its textures pulling together or torn apart by malevolent brass mutterings. At moments the orchestra seemed about to gallop out of control, only to subside into a harsh whisper before finally finding serenity. Lindberg was called to the stage three times to acknowledge the applause. Who says new pieces never get audiences excited?