Just heard Ronnie Laws' cover of "Tell Me Something Good" (Rufus & Chaka Khan had the hit in '74) on WTF (which is back on the air, btw). In looking it up, because I couldn't ID who was covering it, I learned that the song was written by Stevie Wonder. I had no clue.
I think the story was they were recording in adjoining studios and he heard Chaka's voice and wrote her a song on the spot -- which she rejected. So he wrote this one.
I'd believe that. Man, that dude just exuded great songs back then, pretty much like breathing. Wonder what the song was that she turned down?