One of my most prized possessions is the 9 CD box set "The Complete Stax Singles 1968-71". Here are a couple of absolute corkers from 1970:
"Play The Music Toronadoes" - The T.S.U. Toronadoes
"Right, Tight And Out Of Sight" - Branding Iron
Also from 1970, here is a remarkably soulful performance from Melanie - almost as remarkable as the hairstyle that suddenly looms up at 1:55. She is backed by the Edwin Hawkins Singers, which probably helps. I nearly wrote the Stephen Hawkings Singers there, which would have been intriguing if rather less soulful.