The Creekdippers/ Ben Weaver, The Borderline London

With his band the Jayhawks, Mark Olsen was one of alt.country's founding fathers. That was in 1985, and Olsen left his fellow Minnesotans 10 years later to retreat into California's desert, where he lives with his multiple sclerosis-afflicted songwriter wife Victoria Williams (the impetus for the benefit album Sweet Relief).

With his band the Jayhawks, Mark Olsen was one of alt.country's founding fathers. That was in 1985, and Olsen left his fellow Minnesotans 10 years later to retreat into California's desert, where he lives with his multiple sclerosis-afflicted songwriter wife Victoria Williams (the impetus for the benefit album Sweet Relief).

His music since, with his Williams-assisted band the Creekdippers, has slowly shed its rock trappings, to reveal the spartan serenity Olsen has found in the wilderness; the new album, Mystic Theatre, is a blissful distillation of almost amateurish back-porch Americana. A simultaneous new release, though, Political Manifest (as yet unavailable here) is that album's raging flipside, a nakedly political curse upon George Bush. As Olsen's faithful gather tonight, this double-blast of American ideals promises a rollicking show.

My expectations are raised still higher because their support act is fellow Minnesotan Ben Weaver, 24 - a songwriting giant in the making. His lyrics are about the raw mystery of marginal people, full of dirty domestic details and sung in a gravel voice of claustrophobic force. By the last song, "Sway With Me", about the US heartland as its heart is torn out, which he bitterly dedicates to George Bush, he is almost swallowing the mic. "Put the asshole down," he says of his President.

When Victoria Williams introduces the Creekdippers with a speech condemning US tactics in Iraq, a night of rebellious celebration seems doubly assured.

Williams and Olsen certainly make an intriguing couple: she the unpredictable loose cannon, he her helplessly baffled, loving foil. But Olsen's clearly giving nature, though doubtless a marital asset, allows a musical fiasco. "You're pushin' me around!" Williams half-jokes when he physically removes a guitar she shouldn't be playing. Olsen shakes his head, as if she's a child he adores too much to discipline, a costly mistake. Gradually Williams - a marginal songwriter in the Creekdippers - claws greater attention for her earthy asides, errant playing and general naughtiness. Olsen, the man we are here for, literally sinks from sight, squatting at a piano and barely singing, while his wife merrily throws his band into shambolic anarchy. Even on a direct song such as "Portrait of a Sick America", in which Olsen envisions himself beating Bush to a pulp as women vengefully cheer, all emotion is dissipated when, mid-lyric, he moans about sound-levels.

Only at the end does Olsen re-seize the reins of his show. On "Bells of St Mary's", his sweetly strained voice is bolstered, not smothered, by Williams' harmonies. Then, on "The End of the Highway", a spare savaging of Donald Rumsfeld, the band finally play pure Californian honkytonk, and Olsen, hammering the piano, weakly shakes his fist, a soft, good man drawn unwillingly to anger - although, tonight, too late.