Barbra Streisand was the official inspiration behind Bob Dylan's Lay Lady Lay hit, according to an unearthed 1971 'interview' with late blues star Tony Glover.

The two friends exchanged letters, in which notoriously private Dylan opened up about his songs and career, and now the lost correspondence has been discovered and is set to go under the hammer at a Boston, Massachusetts auction.

The letters reveal Dylan, born Robert Allen Zimmerman, changed his name because he worried about anti-Semitism, and wrote Lay Lady Lay for Streisand - a music myth that the singer and songwriter has never publicly addressed.

It has long been believed Dylan wrote the tune for the 1969 movie Midnight Cowboy, but the singer told Glover he created it as a tune for Streisand, without elaborating on the nature of their relationship.

Experts at R.R. Auction, who are selling the letters, claim the correspondence was supposed to be part of an Esquire magazine article, but Dylan lost interest and the piece was abandoned.

Glover, who befriended Dylan when they were both struggling musicians in Minneapolis, Minnesota, died last year, and his widow has now put the documents up for auction.

Bidding is to begin online on 12 November.