The opening song in "O Brother, Where Art Thou?" was a recording of actual prisoners in 1959, and one of the prisoners was tracked down and paid 40 years later.

The opening song in "O Brother, Where Art Thou?" was a recording of actual prisoners in 1959, and one of the prisoners was tracked down and paid 40 years later.

O Brother, Where Art Thou? is a 2000 film created by the Coen Brothers that takes the story of The Odyssey and places it in 1937 Mississippi. In the opening scene of the film, a chain gang is seen breaking rocks while singing a song. It turns out the song was a real track from four decades earlier, and not something made up for the movie. 

In 1959, an amateur singer named James Carter was an inmate in camp B of the Mississippi State Penitentiary in Parchman, Mississippi. He and the others in his chain gang were chopping wood while singing when folk music historian Alan Lomax met them and decided to record the group. 

Carter, credited as the soloist, and the rest of the chain gang, sang an old spiritual song, “Po’ Lazarus,” to the timing of their log cutting. The recording was purchased by the Coen Brothers for their film, which eventually went on to win a Grammy. The Coen Brothers decided to track down Carter, and he was paid $20,000. 

(Source)