Just saw the trailer when I been to the movies last time, but didn`t remember anything special about the music.

The article itself is a bit contradictory about "Roll Jordan Roll" - either it is written by Mr. Britell or just arranged.

Since many old english ballads survived in the rural south I`d imagine that the spirituals being collected by earlier musicologists would have been around for some time before the civil war. Maybe Mr. Britell found a way to get his original music into the movie by claiming spirituals recordd were different from earlier ones?