The protagonist of the work is a white American in early middle age sometimes in blackface, who has a friend who addresses him as Mr. Bones.  
Number 91 is the last of a sequence of 14 entitled "Opus Posthumous."  The first set includes "'The Prisoner of Shark Island' with Paul Muni" and "A Strut for Roethke," while the last of them begins "My daughter's heavier."  The protagonist of the work is a white American in early middle age sometimes in blackface, who has a friend who addresses him as Mr. Bones.  For 10 points - identify this sequence of 385 poems about a character named Henry, a work of John Berryman.
Number 91 is the last of a sequence of 14 entitled "Opus Posthumous."  
The Dream Songs