Songwriting duo Nick Ashford and Valerie Simpson were taking a leisurely stroll through Central Park in '66, looking at the high-rise buildings surrounding the park like mountains, when the iconic words came to Ashford's mind: "Ain't no mountain high enough..."
The real-life couple honed in together on the lyrics to write a love song with a chorus ringing with both sentimentality and strength: "Ain't no mountain high enough/ Ain't no valley low enough/ Ain't no river wide enough/ to keep me from getting to you."
"I first heard the demo in my Motown office in late '66. I liked it," reminisced Motown arranger Paul Riser, a key player who prodded along the song's transformation from its infantile stage to its final studio edits. Working together with Motown's house band, Riser placed the famous rattlesnake sound - tick-a-tick-a-tick - in the song's opening seconds to "build suspense before Tammi's lead vocal came in."
After Terrell's vocals came together with the rhythm track and the horns, producers Johnny Bristol and Harvey Fuqua decided to double down on the song's romantic feel by giving Terrell a musical counterpart. Marvin Gaye entered in on the Terrell record, overdubbing his vocals so that his voice wrapped around hers in a loving duet.
Though the two recorded in separate studios, the duo sang to each other as if they were in love, sparking a musical chemistry between the two singers that would ignite into a beautiful run of hit duets.
The two-and-a-half minute "Ain't No Mountain High Enough" was released through Motown Records in April 20, 1967, scoring Gaye and Terrell a chart entry on Billboard's Hot 100 at No. 19 on July 14 that year. The other dynamic duo in the room, Ashford and Simpson, cemented their status as Motown's secret songwriting weapon with the romantic number while Gaye and Terrell scored their first Top 20 hit together.
The magical partnership between Gaye and Terrell was ultimately cut short with Terrell's tragic decline in health, which became public when she collapsed into Gaye's arms during a 1967 show in Virginia. Though the pair went on to record a few more monster hits for Motown and went back on the road together, Terrell seemed to never have fully recovered her health. She passed away in March 1970, a couple weeks shy of turning 25.