Midway through Vampire Weekend's Thursday night closing set, frontman Ezra Koenig jokingly asked the crowd, "Did anyone take public transportation to get here?" Judging by the hours of traffic it took thousands of cars and RVs to roll into the Bonnaroo campground, not many people did. Still, the preppy pop-punk crew got the crowd riled up with the sparkling pop-rock jam "M79," which Koenig described as their tribute to public transport. Vampire Weekend's set mostly featured tracks from their debut disc, including "One (Blake's Got a New Face)," on which Koenig engaged the crowd for a deafening sing-a-long. But the band were brave enough to unveil a new, still-untitled song, and it might be their most afro-pop-inspired jam yet, with synthesized tribal chants, sparklingly clean guitar lines and Koenig's amped-up hoots and hollers. "If you don't know this song," Koenig told the crowd, "and you're on drugs, all you have to do is dance."