In my opinion, the one man band consists of two antagonist and one protagonist. however, half way through the story, these characters change their characteristics. For example:
The little girl starts off being innocent and gives the impression that she does not know music and is very impressed by both the performing men. however, when she had lost her penny, she became furious and played the violin better than any of the men. for being a protagonist, she became an antagonist as she didn't give any of the men any penny even though she had a bag full.
As for the two men, initially being the antagonist, they try to impress the little girl to get her penny. but in the end, they give the impression of being protagonist as they were not given a penny by the girl. she threw two penny's into the fountain and they had to work together to get the penny's.