Lou Rhodes, Jazz Café, London

The pure joy of singing shines through some country platitudes

The Mercury Prize's initial allure as a music award based purely on merit evolved some time ago into a highbrow version of the Brits. It also had an unfortunate habit of crippling its winners' careers, as they're tainted with its air of worthiness.

Still, the Mercury does reach down each year to bestow its growing commercial clout on unheralded acts such as Lou Rhodes. Though Rhodes has sold a million albums during her decade with the trip-hop band Lamb, Mercury-nominated solo debut Beloved One is hardly hit record material.

It was recorded after she quit both her combustible creative relationship with Lamb's Andrew Barlow, and her deteriorating life with her children's dad, retreating with her kids to a rural commune. It's a contemplative, unexceptional work, deliberately stripped of the thick soundscapes Barlow gave Lamb. Its nomination is frankly hard to explain. Seeing Rhodes play her first gig since its announcement, though, makes things much clearer.

"No Re-run" is Rhodes' first song, summing up the "life isn't a rehearsal" mantra she lives by now. Her huskily pure voice is the first asset you notice; its cleanly piercing quality reinforced by Rhodes' almost shark-dark eyes, which peer out, assessing her crowd. With her white frock and long hair, she looks unsettlingly like a prettier Sissy Spacek in Carrie, waiting for the pigs blood to fall.

With a double bassist and violinist among her acoustic combo, faint traces of Nick Drake's English chamber-folk and 1950s cool jazz are inevitable. When Rhodes sips from a Thermos of tea, as she's handed a guitar seemingly made from a piece of wooden cupboard, she could hardly be more homespun.

The harder, bouncy beats of "Fortress" (about a combustible couple who, Rhodes happily notes, wept for a day when they heard it), show a tougher side. "Tremble", released as a single post-Mercury - "might as well make the most of it!" she accurately notes - then sees her close-eyed and ecstatic. "Inlakesh" and "Each Moment New" complete her musical range, letting the band cut loose into a jazzy improvisation and cultural exoticness barely present on record.

If anything, one of several brand new songs, "All We Are", lashed forward by cymbal rim-shots, is more forceful still. The problem withBeloved One as an album is that it expresses the simple security of Rhodes' new life too well, coming across as a sequence of rustic platitudes, the raw feathering of emotional ties that preceded it seemingly already cauterised.

Live, Rhodes reopens those wounds, as on "To Survive", where the aftermath of love is recalled as "the worst kind of nothing". ForBeloved One, backed by a shiver of strings, she lets out apparently effortless, cavernously vast cries, lost in the pure joy of singing.

If it's still all a little too cool and controlled, the long-time Lamb fans filling the Jazz Café closed their eyes in epiphanies anyway. They'll still be watching Rhodes, long after the Mercury circus has gone.