The term "post-rock" conjures up a number of images in the mind's eye, chief among them fierce beards, intense expressions and nodding heads. Bands like Mogwai and Tortoise currently shelter beneath its awning, constructing complex songs that take a free verse approach to the traditional metres of rock music.

Billy Mahonie are an emergent member of this breed, a London-based group whose name unites its members in the persona of one small boy. Perhaps fortunately, this concept receives no further encouragement from the music they play, which instead adulterates various traditions of guitar music. They have no singer, only one (rather fetching) beard and create meandering instrumentals of some loveliness, punctuated by savage, noisy asides.

This was the launch party for their first album, The Big Dig, which succeeds in making songs from a series of Sonic Youth-style digressions and crafts a pleasantly rockist mood music. The sound was cranked up tonight, but they did not sacrifice the more introspective elements of their music. The lava lamps festooning the stage at any rate gave the audience cause for reflection, as did requests for those at the front to sit down. As fugs of cigarette smoke billowed up from the crowd, the impression of a 60s-style underground happening became irresistible.

This was not, however, an evening to match the pretentious highs of those heady days. Less a bleeding edge symposium on guitar experimentalism and more a showcase of accessible songmanship, Billy Mahonie were hellbent on taking the opposite path to haughtiness.

However intricate the interplay between guitars became, the songs themselves were leavened by a winning sense of melody. We Accept American Dollars was an ambient rock number of great charm, while Drago had a pastoral, lilting edge to it. Elsewhere, Hoon (their first single) took a glance at the blues, before heading off in search of noisier nourishment; William Derbyshire, too, built itself insistently towards a guitar wig-out of unbridled ferocity.

The quartet, like their songs, periodically explode into life with frenzied bouts of action. The intimacy of the venue also meant the more involved moments of their musicianship didn't lose people's interest. By the end, the many nodding heads among the audience signalled a deserved approbation.