"Inspired" by some of the posts above, I just had a listen to the "United", "You're All I Need" and "Easy" albums. "United" is all Marvin and Tammi, and I would suggest that the "YAIN" album is also all Marvin and Tammi with the exception of the title song [[and it pains me to say it) since the female vocal on "You're All I Need To Get By" and "Good Lovin Ain't Easy To Come By" sound very much the same to me then it's Valerie Simpson. It sounds to me like Valerie on all the harmony parts with Marvin, and if Tammi is on it at all I would suggest just the verses OR verse and harmonies with help from Valerie. As regard "Easy", I would agree that aside from the 2 obvious Tammi songs, the rest are Marvin and Valerie. Just an opinion, of course!