The Followill men have a winding history with Lollapalooza; they hit the road in its 2003 tour, during which they happily sabotaged a rival act, and headlined the festival in 2009. Perhaps that familiarity is what prompted the methodical Southern rockers to go off the rails —relatively speaking, at least — in the encore of their Sunday headlining set. They began by ushering out a classical string ensemble for a dramatic take on "Crawl" (from their 2008 breakthrough album Only By the Night), violins scraping against their beefed-up psychedelic guitars and singer Caleb Followill's guttural screams. Then, amid autumnal violet lights, they launched into a cover of Robyn's "Dancing on My Own," Followill sighing along with melancholic torpor over the guitar-thick power balladry. The experimentalism suited them.