O Brother, Where Art Thou is a favourite movie here.
The Peasall Sisters provided the singing for the characters the Little Wharvey Gals, even though George Clooney was their paterfamilias.
Here are a variety of renditions of Angel Band.
First, briefly, from the O Brother soundtrack. (this features vocals by Robert Hamlett as well)
Secondly, a 2007 rendition (the video is completely out of sync, so close your eyes)
Thirdly, a 2011 interview with them about the original recording experience in which they provide a taste of how they sound some ten years down the track – begins at 2.20. (The first couple of minutes deals with Dan Tyminski’s recording of Man Of Constant Sorrows)