Actually, the blues singer that Ry Cooder WAS friendly with was Sleepy John Estes. Cooder used to play a lot of his tunes in concert when playing solo, playing blues mandolin in the style of Estes' long time friend and sideman Yank Rachell. On the album "Boomer's Story", Cooder not only plays Sleepy John's "Ax Sweet Mama" but lets Estes himself sing his "President Kennedy" while Ry plays mandolin along with the singer's guitar. Ry did "Going To Brownsville" on his first album and a recording called "Acoustic recording at Radio Ranch 12/12/72" put out in 2014 on the Echoes label of a radio concert in Cleveland OH, he sings "Brownsville" as well as two other Estes songs on solo mandolin, "Clean Up At Home" and "Floating Bridge".