Prophets of Rage were all set to played in the California Rehabilitation Center in Norco, Calif., when their show was canceled. Instead, the supergroup comprised of members of Rage Against the Machine, Public Enemy and Cypress Hill set up their gear outside the prison and blasted the music loud enough for the inmates to hear through the walls.

The concert was to support Jail Guitar Doors, an organization founded by Wayne Kramer of the MC5 and Billy Bragg that helps rehabilitate prisoners by providing musical instruments to them. Jail Guitar Doors is named after a 1978 song by the Clash that deals with Kramer’s 1975 conviction for selling cocaine.

“We were denied at the last minute because apparently they got some calls from right-wing nuts in Sacramento who said they were going to foment rebellion,” guitarist Tom Morello told CBS Los Angeles. “What we meant to do is come here to play a great show.”

For Kramer, having the California Department of Corrections deny the inmates the opportunity to hear the band is part of the problems inherent in the system. “They didn’t want to see good things happen for what they consider to be bad people,” he said, “when in truth, they’re just people.”

Morello points out that reasons like that are precisely why the band exists. “We play for those on the lowest rungs of the ladder,” he added. “We play for the underclass, those who do not have a presidential candidate who represents them. …The barbed wire cannot keep the music out. The barbed wire cannot keep the message out.”

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