The guitarist of the picture probably sang at the Canja de Viola of TUC (Universitary Theater of Curitiba) and decided to continue the show at Tiradentes Square. From the bus I could not hear him, so I can not say whether the music was good or not. The Canja de Viola is a permanent show of Brazilian Country Music, it takes place at TUC since 1985.
A little translation: "Canja" in portuguese has different meanings. The main one is "chicken soup with rice", but it may also means "something easy" and in musical terms it means "a sample" or "a short performance".