Check out this Brenda Holloway song.
http://www.npr.org/programs/asc/archives/asc24/index.html#holloway
Hey, eleni, that's pretty good for unreleased material, isn't it? They had a surplus of the stuff back then; it's kind of nice hearing something for the first time that was made in 1965.
From (I think) 1964 there was a good Motown duet with Marvin Gaye and Mary Wells called "Once Upon A Time." I never hear it played as an oldie, which of course you can say about a lot of great songs.