Margo,
i sang 'down in the river to pray' a capella and they loved it, there are some other changes if you listen closely. the words change a bit in each verse and there are 2 versions of the chorus...'starry crown' or 'robe and crown'...
you can also do some variations on the tune, go up on some parts for intensity, do some note shaping.
anyway, it was very well received when i did it. not everyone knew it, surprisingly, though i and some others have been raving on about the movie and music since it came out.
*caiti*