Mildred Woodard
Hidden in the vast and highly regarded blues catalogue of Nashville's Excello vaults there are some wonderfully obscure southern soul gems like the one from Joe Mayfield. Another one is this amazing deep item from the obscure Mildred Woodard. 
I've Waited So Long has an astonishingly tough vocal from Ms Woodard just check out that gruff throaty roar on the refrain. Awesome. The backing is classic southern stuff featuring some good triplet piano, strong horns and nice guitar touches. But the real treat here is the voice - and that's how it should be.
Note ~ "I've waited so long" can be found on the rather strange Ace UK collection "Blues for hippies".