the grateful dead
The Grateful Dead is, or rather was, a psychadelic rock band, consisting of the members Bill Kreutzmann, Ron "Pigpen" McKernan, Jerry Garcia, Bob Weir, Mickey Hart, and Phil Lesh. The Grateful Dead formed in the year of 1965, known for their eclectic style that fused elements of rock, blues, jazz, folk, country, bluegrass, rock and roll, gospel, reggae, and world music with psychedelia, the band is most well-known and famous for their improvisation during concerts, and their strive to make every concert different, changing the tune or tempo of some songs when they played, and are considered the godfathers of the jam bands world.
Their devoted fanbase, known as 'Deadheads', would follow around the Grateful Dead, and is maybe one of the most loyal fanbases I've ever seen. I've been one for life, raised by my sperm donor as a Deadhead from birth, and he's been one for as long as he can remember, really.