Ain't No Mountain High Enough — Marvin Gaye and Tammi Terrell (1967)

Ain't No Mountain High Enough pairs a thrilling call-and-response structure with a seismic emotional punch, making it the definitive soul duet template. Written by Ashford and Simpson in 1966, Gaye and Terrell's recording soared to #19 on the Billboard Hot 100 and #3 on the R&B chart in 1967, outperforming the average Motown single of the era by nearly 20 chart positions. Terrell's tragic onstage collapse just months later—caused by a brain tumor—imbues every soaring harmony with a poignant finality, cementing this track's legacy as the genre's most powerful vocal partnership, outlasting even #2 Gaye's solo work in raw collective chemistry.