Samuel L. Jackson learned to play the guitar for this film, while completing production of Snakes on a Plane (2006). This film was the other of two films released the same year that Jackson starred in with the word "snake" in the title.
Cedric Burnside and Kenny Brown, the members of Lazarus' band, are the grandchildren of legendary (but relatively unknown) blues singer R.L. Burnside. They played in his band while he toured up until his death in 2005. Additionally, the reverend (played by John Cothran) is named R.L. On a side note, features of Lazarus (played by Samuel L. Jackson), such as his hair and his history with the Juke Joint, are remarkably similar to Burnside's.
The trivia item below may give away important plot points.
Rumor has it the original ending involved Justin Timberlake's character shooting Samuel L. Jackson in the back of the head during the scene where Christina Ricci sings "This Little Light of Mine". Director Craig Brewer decided, however, that it would be better to make the film happy, and with a very positive ending.