Pop: Ben Harper; Jazz Cafe, London

Hyperbole is no stranger to the popular music industry, at least that branch of it given over to descriptions of the latest performers - but in Ben Harper, breathless expressions of adulation may have finally found a suitable home. Now aged 25 and with two albums under the belt of his combat fatigues, the Californian singer/ songwriter is something of a rare bird: a virtuoso slide guitarist who blends blues and protest songs with a presence and a vocal range that belie his tender years.

Harper may not have yet cracked the mainstream market, but it's reasonable to assume that that is only a matter of time. Last year's album, Fight For Your Mind, is an accomplished piece of work, and Harper's live performance, a mix of streetwise savvy and passion, has sufficient verve to ensure a glittering longevity.

Even so, it's against some odds. Slide guitarists, Ry Cooder notwithstanding, don't exactly spring to mind when one's thinking about axe heroes. Harper, who certainly counts Cooder's sly, twanging soundscapes among his influences, alongside Jimi Hendrix, Bob Marley and Richie Havens, was aided by the enforced intimacy that small venues such as this offer. Seated on a low stage (indeed, to the palpable delight of those not immunised against the singer's sultry good looks, virtually in the audience), Harper coaxed his vintage Weissenhorn guitar - a hollow-necked acoustic instrument fitted with an electric pick-up - into conjuring up sounds that stretched the imagination. It was, simultaneously, a percussive tool, a fuzzed-up funk engine, something capable of blending the most subtle nuances with an urgent ringing.

Harper has much to be urgent about. Songs such as "Like a King", written in the wake of the LA riots, and "Excuse Me Mr" deal with fundamental civil rights. Elsewhere, his language is peppered with images about personal freedom and environmental concerns. There are a lot of clenched fist salutes, not just from Harper, but also his three-piece band: the sublime bassist Juan Nelson, percussionist Leon Mobley, and drummer Oliver Charles. Harper may be adapting Marley's role as the righteous militant for the Nineties, but he is doing so with considerable style and panache. Nevertheless, the fluid quality of Harper's performance militated against any sense of over-staging. His opener, "Oppression", segued into Marley's "Get Up, Stand Up", then a mighty Latin break, all of which made it clear that Harper is a musician who goes where his grooves take him, and he has the power and the control to tease the ensuing drama to the full.