There may be no American musician more ripe for the documentary treatment than Roky Erickson. There’s the tale of great promise in 1966 as the 13th Floor Elevators invent psychedelic rock and gain a reputation as the most other-worldly group alive. There’s a long period of reinvention as he continues to produce great stuff – cryptic and haunted though it is - into the 1980s. There’s a backstory of madness and decline. There’s even a......