The self-taught, Dave Brubeck-influenced guitarist and singer has a long and storied career. “In the 1970s and early ’80s, when Brazilians lived under a harsh military dictatorship, he and his lyricist, Aldir Blanc, empowered them with songs that conveyed intense pride and fighting spirit. The messages were often encoded to fool the censors; Mr. Bosco’s lilting tunes and rhythms made every song seem to float.”