Polar Bear @ The Arches, 21 Jun

A passing Duke Ellington fan may not recognise it as such, but in the case for jazz being about embracing creative freedom and pushing at accepted forms, Polar Bear should be Exhibit A. Tonight a ruminative opening piece thankfully doesn't set the pace; in light of what's to come it's more a palette cleanser, a Zen exercise in forgetting any other music you might have heard earlier in the day.

Then martial beats strike up, a reggae rhythm starts on John Burton’s guitar, and twin tenors stomp in like marauding conquistadors – this is visceral, meaty stuff. Drones and tense rhythms build to unbearable levels then suddenly resolve into glorious shards of harmony, like some tyro horror director letting the good guys win at the end.

Just when you think they forgot to pack their sense of humour, Burton shows he can shred as hard on a party balloon as he can on a Strat. And you really haven't lived until you've seen a double-bassist like Tom Herbert employ an effects pedal to duet with himself. On tonight's form, Polar Bear are stone cold killers. [David McNally]