Veloso had won a major song prize at the previous year's Festival, when he was backed by an Argentinian rock band, and although his unconventional performance caused some initial consternation, he managed to win over the crowd and was feted as a new star of Brazilian popular music. By late 1968, however, Veloso was fully immersed in the Tropicalia experiment, and his performances, which were expressly intended as provocative art "happenings", caused a near-riot. In the first round of the competition on 12 September, Veloso was initially greeted by enthusiastic applause, but the mood quickly changed when the music started. Veloso came on dressed in a bright green plastic tunic, festooned with electrical wires and necklaces strung with animal teeth, and his backing band Os Mutantes were also dressed in similarly outlandish attire. The ensemble launched into a barrage of psychedelic music, played at high volume, and Veloso further outraged the students with his overtly sexual stage movements. The crowd reacted angrily, shouting abuse at the performers and booing loudly, and their fury was only exacerbated by the surprise appearance of an American pop singer, John Dandurand, who joined Veloso on stage and grunted incoherently into the microphone.