Filmed last year in the ornate setting of San Francisco’s Great American Music Hall, Boz Scaggs runs through an effortless set of his best-known songs from Lido Shuffle to Low Down. In truth, there’s not a lot to watch other than a bunch of middle-aged musos flexing their jazz and blues chops. But when they enter the zone on such extended work-outs as “Loan Me A Dime”, the effect is transcendental.