Did Ray Bradbury know Brun Campbell personally, and did he ever write up a profile of Campbell?
Brun Campbell (1884 - 1952) was an itinerant ragtime pianist in the early years of the twentieth century. He met Scott Joplin and took lessons from him, later calling himself "Scott Joplin's only white student." Later he became a barber, settling down in Venice, California.
Sound familiar? It does if you've read "Death is a Lonely Business".
The character of Cal the Barber in that book boasts of his association with Scott Joplin with little evidence to back it up. In reality, Brun Campbell had a tendency to exaggerate which undermined his credibility, but historians have established that he almost certainly did take lessons from Scott Joplin. Campbell made some private recordings of his own piano compositions.
Ragtime historians would be very interested in any information about Brun Campbell by someone who knew him.
I think that Ray lived in Venice during the time Brun Campbell had the barber shop. The only way Ray would have known his story is by personal acquaintance. I wouldn't be surprised if the depiction of the barber shop in the book is perfectly accurate -- but only Ray can tell us that.