"Johnny Cash at Folsom Prison" is often referred to as the best live album ever, it's true that it captures something unlike any other live album your are ever likely to hear. In 1968, Cash performed a set list of songs about prison, murder, adultery, drugs,,, to a captive audience of 2000 inmates who fully appreciate his macho rebel spirit. When he sings "i shot a man in Reno, just to watch him die" he gets a cheer and a whoop from the audience.
Throughout the recording he makes jibes at the prison staff, implies he's on cocaine, and swears (which had to be bleeped out on the original release). Johnny Cash was punk rock before it had even been invented...
You can read the album liner notes by steve earle here.
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