IT'S the mark of a special band that it can keep surprising its audience all the way to the end of a gig. That's what pianist Chick Lyall and saxophonist Rob Hall did here, continually finding different routes for their quartet to explore. As well as playing robustly melodic saxophone, Hall is the spokesman introducing a repertoire that, in the first set, began with Steve Swallow's elegantly twisting Falling Grace and ended with Hall's own Pied Piper, which puts a dancey bounce into the steps of Hamelin's exiting rats. Lyall's contributions come entirely from the page and the keyboard. A player who occasionally appears to slip off the radar, he always returns with his considerable talents enriched. He long ago absorbed the more gospel influenced, down-home side of Keith Jarrett and the folk tradition- inspired romanticism of Bobo Stenson into a flowing, investigative style of his own and the resourcefulness that results created a string of solos that had this listener, at least, hanging on to every final note of resolution. His compositions come from various sources of inspiration and in that regard complement Hall's splendidly. The second set found them recreating Hall's Bizzyberry written for the Biggar Big Band, in a guise that updated Jarrett's Scandinavian quartet, exploring free improvisation with clarinet, a boogaloo beat and a bebop pay-off, and rattling through a jazz jig before ending with a rare jazz quartet reading of Ralph Towner's gorgeous Icarus. They were helped no end by bassist Jennifer Clark lending sure backbone and Andrew Bain's beautifully restrained drumming in another triumph for the new Bridge Music Glasgow Jazz Series.