Foster's Social Orchestra, which performs in the film, was founded by Michael Nyman as a group attempting to create a post-modern, avant-garde sound by having artists with a background other than music perform the works of Stephen Foster in an untrained but inspired way.
The trivia items below may give away important plot points.
According to Robert Carlyle's DVD commentary, vegetarian Guy Pearce stoically underwent multiple takes of him eating the life-saving Knox stew (which was in fact a very nice lamb stew prepared by the film's caterers). Chomping into large chunks of meat and then spitting them out as soon as Antonia Bird called 'cut'.
The end fight was made up by actors Guy Pearce and Robert Carlyle when the original scripted ending (which was to take place on the roof of the cabins at night while they were burning) was scrapped in favor of them just beating the hell out of each other. During this, the production ran out of fake blood.