One usually has to wait until the fourth movement of a Bruckner symphony before one gets a decent, foot-tappin', knee-slappin' polka to dance to. But at last night's Prom Osmo Vänskä was jitterbugging - and, I think, even moonwalking - from the off, swinging his classy Minnesota Orchestra into the Fourth Symphony's opening fortissimo brass triplets like they were a seasoned jazz band, and making Bruckner boogie. Not the easiest of things to get this granitic old Austrian bumpkin to do.