Firefly is not an EDM festival, but it wouldn’t be unfair to characterize its denizens as EDM kids — or maybe only half-EDM kids, with Bud Light bottles in backpacks instead of acid tabs and molly. But for an hour on Saturday afternoon, even the more stereotypical festival bro was grabbin’ a pardner to do-si-do in the middle of the mud to Sturgill Simpson, who’s really an anachronism at this particular festival. While modern country has fused with EDM and homogenized with hip-pop, Simpson keeps alive the spirit of lone-wolf, hard-travelin’, traditional country — all amid a wash of club DJs and pop generalists. His set is ferocious but fun and impeccably sequenced, blending frisky barroom jams with lower-key balladeering in pairs of two. One of the Firefly crowd’s biggest strengths is finding what they like in the acts they don’t know. In Simpson, they found a good time, and I’d bet he found the same in them.