Successful pianist murdered by villain The Phantom Troubadour in the "Troubadour of Terror" story in The Human Torch comic book, Vol. 1, #31 (July, 1948). Borsch is giving a yacht party when the Phantom Troubadour shows up and shoots him dead.
He's likely Russian, given Borsch is a reference to the regional dish borscht.
The song's title, "Death in Venice," is taken from the 1912 novella of the same name by Thomas Mann.