Marvin Gaye & Tammi Terrell - Ain't No Mountain High Enough

You can't have a Marvin retrospective without mentioning Tammi Terrell. Sure, he duetted with Kim Weston before and Diana Ross after (ironically he and Ross did not get on at all in their recording sessions), but the Marvin-Tammi sessions just sizzle off the vinyl; rumour has it they were more than just friends and the fact is that the chemistry between the two is there for all to see. Whatever the truth, it made for some fantastic music.
Written by Nick Ashford & Valerie Simpson (as in Solid & California Soul) Mountain is possibly the most perfect pop song ever made.