Outside Austin, Texas, a 53-year-old man sits in an apartment with four radios, three televisions, two amps, a radio scanner, and an electric piano playing. At the same time. Loudly. He has three teeth, his hair is matted into one huge dreadlock, and he has a notarized document on his wall declaring himself an alien, "so whoever's putting shocks to my head will stop." Thirty years earlier, Roger Kynard "Roky" Erickson was a rock-and-roll icon: A manic singer who was Janis Joplin's primary influence, he fronted a band called the 13th Floor Elevators, considered by many to be the creators of psychedelic music. After a 1969 marijuana arrest, Erickson entered an insanity plea and was sent to the Rusk State Hospital, a medieval institution deep in the east Texas pineforests. He remained there for three years with the state's most violent mentally ill offenders, then reemerged a changed man: He sang about ghouls, zombies, and Satan, christened himself "the evil one," and declared himself an...