Beth Gibbons and Rustin Man, Academy, Bristol

Before she formed Portishead with Geoff Barrow and made Dummy, one of the greatest albums of the Nineties, the singer Beth Gibbons auditioned for a place in O'rang, the group formed by the bass-player Paul Webb after his departure from the ambient Eighties outfit Talk Talk. Last year, Webb and Gibbons finally saw through their long-awaited collaboration – with Webb appropriating the peculiar pseudonym Rustin Man, after one of their songs – and produced the quietly elegant Out of Season.

When I say "quietly", I mean "very, very quietly". Largely acoustic, the album is a collection of spookily intimate folk ballads backed by the sparsest of arrangements – a hint of violin here, a splash of accordion there. There is none of the restive trip-hop beats that provided the framework for Gibbons's kooky vocals in Portishead.

Indeed, in that respect, Out of Season is gloriously out of step with the musical fads of recent decades. Live, the subdued nature of the songs could easily work against Gibbons and Webb, but tonight they've fleshed out the instrumentals, and the stage is replete with guitars, cellos, violins, keyboards and drums.

"Mysteries", a reflection on the vagaries of love, opens with the ghostly sound of the melodica and is full of brooding melancholy. "Tom the Model", augmented by a ghostly choral backdrop, is loud and expansive, while "A Funny Time of Year", a paean to the ebb and flow of nature, brims with melodrama.

Gibbons's voice is an extraordinary instrument, managing to sound at once vulnerable and scary. One minute, she's singing with the elegance and sobriety of Billie Holliday; the next, she's stretching the vowel sounds to breaking-point and spitting out words as if she had a mouthful of grit. Being watched by an audience of hundreds clearly isn't among Gibbons's favourite occupations. Indeed, as the night goes on, it's clear that for her, live performance is on a par with medieval torture.

Hunched and awkward, she hides behind her hair for most of the night and, in between songs, stares fixedly at the floor. In one instance, she even sticks her finger in her ears to block out the applause. Still, the singer's generally crucified expression doesn't detract from the music, which remains hauntingly intense from start to finish. It seems that Gibbons's pain is our gain.