An old western called Django. Which Django Unchained obviously pays homage to and uses the song in the credits/opening scene. I don't see your point.
However, I will say that the composer of the song, Ennio Morricone, is brilliant. Look up any of his songs on youtube specifically Dies Irae Psichedelico, Ombre Chiare, or Harominca if you like the Django song.
Yo the KZA, the Ray-Zah, Lyrical assassinatah