Lots of tunes by the Sweet Inspirations, whose roots were in gospel (via The Drinkard Sisters): http://en.wikipedia.org/wiki/Sweet_Inspirations .
Kas, on Black A Kill Black, your guess is as good as mine. On the Heptones, there's even an album called Alton Ellis Sings, the Heptones Harmonize.
Martin, I beg to demur as far as Aretha's version of Bridge... (complete with backing vocals, quite possibly by the Sweet Inspirations, and King Curtis on sax; nice guitar too) is concerned:
http://www.youtube.com/watch?v=H9VrCSPPhdE
- and her version of Let It Be, for that matter:
http://www.youtube.com/watch?v=w09Jcjj_QOI
