The central image in "Brassed Off'' is that of a face: shiny, homely, dead serious. It is the face of a man who earnestly believes he is doing the most important thing in the world. The man's name is Danny, and he is the leader of a brass band made up of coal miners who work at a pit in Grimley, a Yorkshire mining town. The band was founded in 1881, and its rehearsal room is lined with the photographs of past bandmasters, looking down sternly on the current generation of musicians.