I had always known that the popular versions of In My Time Of Dying and Death Letter were reproductions of old blues songs, but I knew very little beyond that. I decided to do a little investigatory work on these two songs, and here is what I found.
Study #1 - In My Time Of Dying
In My Time Of Dying is based on the song "Jesus Make Up My Dying Bed", originally recorded by Blind Willie Johnson. Blind Willie was a "street preacher" and slide guitar player from Texas. He is credited by many including Eric Clapton and Keith Richards as being the finest slide guitar player who ever lived. In My Time Of Dying has been recorded and reinterpreted by numerous artists, including the ones below. It is amazing to me that something so influential originated in Marlin, Texas.
Study #2 - Death Letter
from wiki... "Death Letter", also noted as "Death Letter Blues", is the signature song of influential blues musician Son House. It is structured upon House's earlier recording "My Black Mama, part 2" from 1930. House performed the song on a metal-bodied National resonator guitar using a copper slide. "Death Letter" is Son House's most famous song, and was the centerpiece of his live performances during the blues revival of the 1960s. House often altered the tempo and lyrics for different performances of "Death Letter", occasionally playing the song more than once during the same concert. Some renditions exceeded fifteen minutes in length.