Marilyn McCoo of the Fifth Dimension (although I think she had a bit of a career separate from them, as well).
Not quite the voice that Karen Carpenter had, but a wonderful reminder that it was perfectly acceptable for black performers to aim solidly at the mainstream of American culture. I don't know much about her, except for hearing an interview a few years ago where she seemed to be going out of her way to distance herself from what ghetto black culture has become.
While she didn't sing "Day by Day" in the movie Godspell (1973), the Fifth Dimension's recording of it is the one that most people know. It is certainly the one that I knew at a time when I had classmates witnessing to me about Jesus, but I wasn't paying attention.
I think I need to get a Fifth Dimension greatest hits album. I can convert the sound tracks of these YouTube videos, but it would cheat some very talented people out of some money, and the sound quality isn't quite as good, either.