It’s something else entirely when a character in a film actually performs a song. When dialogue and plot progression stop to pause for a song, the weight is significant. In O Brother, Where Art Thou?, Chris Thomas King makes the most out of that pause to play a quiet, traditional, hard-hitting blues track. Playing a character inspired by Robert Johnson, he delivers Hard Time Killing Floor Blues (originally by Skip James) with a deftly downtrodden hand. It’s the sort of soul-scraping performance that the blues is supposed to be about. Confident and despondent at the same time, it’s a weary, knowing lament delivered with a clear voice, a slightly modern guitar lilt and a healthy respect for the folk traditions in which the song is based.