The last night of the Vortex club's F-ire Collective festival gigs was appropriately left to one of that loose-knit organisation's most celebrated offspring - Polar Bear, the two-sax quintet that's been described as sounding like Tom Waits translated as a free-jazz instrumental. The band played two nights, a kind of dolorously wayward Christmas party, with various like-minded guests.

Polar Bear played exuberantly hard and fast in the opening show on EST's London Jazz Festival performance (drummer Seb Rochford thought the digression from their usual methods was more likely to have been the result of nerves rather than tactics), but Monday's gig represented the many levels of this innovative group's music. A theme that sounded like Jingle Bells played as a kind of ambient free-jazz eased into slowly winding sax lines and looping phrases from tenors Pete Wareham and Mark Lockheart, playing hypnotically out of phase with each other. Rochford's soft drum sound and delicately arrhythmic toms and bass-drum accents rubbed gently against a quietly funky bass ostinato.

A typically stealthy overture quickly turned into a howling, high-register tenor exchange (with equally ferocious, Jurassic Park-like electronic hollering from fifth member, Leafcutter John), and a rumbling tom-tom figure like a 21st-century Gene Krupa intro presaged a saxophone tussle between Wareham and a spikily agile Ingrid Laubrock, guesting in the second set.

Polar Bear's uncannily hip use of space, surprise and delay began to get increasingly effortless. Short sax blurts followed by silences would be picked up by the gifted Rochford with a shuffle or a hi-hat swish; an electronics crash would be followed by another cliffhanging pause, then they would all cruise off into a lopsided conversational swing. It was elegant and edgy at the same time, and a packed house of all ages testified to the effectiveness of the message.