When Marvin Gaye and Tammi Terrell stepped into the studio in 1967 to record “Ain’t No Mountain High Enough,” magic happened. Their voices blended so effortlessly, it sounded like they’d been singing together forever—even though this was their very first duet. What makes the story even more powerful is their genuine friendship: Marvin admired Tammi’s energy and spirit, while Tammi trusted Marvin’s calm presence. Backed by Motown’s Funk Brothers, their chemistry turned Ashford & Simpson’s lyrics