I must now come out of the closet, I am a burnt cork artist myself.
Since we seem to have gone over to the show itself as a subject, let me tell you what I know.
In the early days there were several parts to any show.
Music, with humor Solos Skits or short plays More music or solos Finale or walkaround
This could change depending on the year or the troupe.
The standard players were the musicians themselves with only the two "end men" (bones and tambo) playing a character as it were. These were the men who delivered the punch lines to the jokes or got a new joke started.
Mr. Interlocutor is a post Civil War invention. In later years he was not blacked up but rather stayed as a white performer. It needs to be known that the stage changed very much over the years. This character is not the only change.
In the 1840's, the show was based on 4 men. In the 1850's the numbers grew to as many as 8 or 10. By the 1880's as many as 40 or more! But in the 1860's there was a revival of the "old time" 4 man shows!! Kind of like the 1970's revival of the 1950's.
In later shows the joke segments and skits were interspersed with music and solos. The bones and tambo however, never changed position even into the 1920's.
Racism is another change in the shows. The early shows were not very racist, they were VERY sexist, but that did not change. By the 1920's racism was the mainstay of the stage. This was also the time when the shows went from the professional acts to an almost all community theater/civil club show. As this change slowly took place over the years, racism took over. Most of the racism that minstrel critics point to did not come about until after 1890.
With luck, this shared heritage will come back, not as pure entertainment, but as educationb as to our shared culture.