The spirit of the '60s abides among improvising rockers—a.k.a. jam bands—and their open-eared fans. The style was forged in the storytelling guitars and jazz-caliber interactions of groundbreaking combos like the Grateful Dead and the Allman Brothers Band, who codified the two-set, ever-changing-setlist format that nearly every subsequent jam band adheres to. Vermont quartet Phish inherited a hefty portion of the Dead's audience following Jerry Garcia's death in 1995, and they delivered the goods with strong songwriting, brilliant group improvisations and an unpredictable prankster spirit. New York's Blues Traveler and the Spin Doctors enjoyed hit singles, while techno-rockers the Disco Biscuits and double-guitar demons moe. hewed closer to their acid-rock forefathers. As Widespread Panic mined Southern rock's rowdiness and gothic sensuality, Colorado's String Cheese Incident and Leftover Salmon imported bluegrass into the electric mix. And Umphrey's McGee, the least crunchy of the pack, added a touch of emo to their riff-based heavy prog rock.