Daniel Johnston
Anyway, a manicly depressed outcast from a religious family in Texas who produces some of the most earnest music possible.
Roky Erickson
Another mentally ill musician with a cool documentary. Erickson's mental instability was largely influenced by drugs whereas Johnston always seemed a bit deranged. Once the stud in The 13th Floor Elevators, Erickson went off the deep end and spent years in and out of hospitals. Some of his work has been recorded from the mental hospital and some out. Like Johnston, Erickson's music focuses on good and evil, with a large part of his career seeming to be downright satanic. Below is the trailer for his film and a nice non-evil track by him.