The song was written by Ashford and Simpsonprior to joining Motown. British soul singer Dusty Springfield wanted to record the song but the duo declined, hoping it would give them access to the Detroit-based label.
As Valerie Simpson later recalled, “We played that song for her (Springfield) but wouldn’t give it to her, because we wanted to hold that back. We felt like that could be our entry to Motown. Nick called it the ‘golden egg’.” Springfield recorded a similar verse melody in “I’m Gonna Leave You” on Dusty.
In spring 1970, after the Top 20 success of her first solo single, “Reach Out and Touch (Somebody’s Hand)”, Ashford and Simpson had Ross re-record “Ain’t No Mountain High Enough”. Initially, Ross was apprehensive, but, was convinced to make the recording.
The remake was a complete reworking of the song, featuring a style similar to gospel with elements of classical music strings and horns, and spoken word passages from Ross. The Andantes, Jimmy Beavers, Jo Armstead, Ashford & Simpson and Brenda Evans and Billie Calvin of the Undisputed Truth were used as backing singers, giving the song a soul and gospel vocal element.
Ross’ version of the song was released on July 19, 1970 as the second and final single from her solo self-titled 1970 debut album by Motown. It is also featured in the 2005 film Chicken Little (2005 film) and the soundtrack of the same name.
Motown chief Berry Gordy did not like the record upon first hearing it. He hated the spoken-word passages and wanted the song to begin with the climactic chorus/bridge. It was not until radio stations nationwide were editing their own versions and adding it to their playlists that Ashford and Simpson were able to convince Gordy to release an edited three-minute version as a single.
Ross’ version of “Ain’t No Mountain High Enough” rose to number one on both the pop and R&B singles charts. Ross received a Grammy nomination for Best Female Pop Vocal Performance. The song is performed in the key of C minor for most of the song, changing to F sharp major towards its conclusion. Wiki