Proceeds from the project, released ahead of Friday's Manson documentary on ABC, will benefit California environmental nonprofit Air Trees Water Animals.

Half a century ago, a few years before Charles Manson ordered his followers to kill a houseful of people in 1969, the young guitarist was serving time in prison for forging checks, writing folk songs by the dozen.

Once out, Manson chased his dream of securing a record contract. Neil Young tried unsuccessfully to get him signed to Reprise. "He was quite good," Young wrote in Waging Heavy Peace. Then the Beach Boys befriended Manson and recorded one of his songs, which charted in 1968. But a record deal eluded him; despite his connection to Beach Boys drummer Dennis Wilson, Manson failed to convince record producer Terry Melcher to take him seriously.

Manson's music has since existed mostly in bootleg form. Now, ahead of an ABC documentary on Manson airing Friday (March 17), a tape he made while at San Quentin prison in the 1980s is available as a limited vinyl package. Walking in the Truth cleans up the rough sonics of the cassette release, says Danbury, Connecticut-based musician and record collector Malcolm Tent, who produced and pressed the LP to help benefit the California environmental nonprofit Air Trees Water Animals, known as ATWA.

"I wanted to make a tasteful package," Tent tells Billboard. "With me, there's a huge fascination with uncovering these lost nuggets, especially from what's come to be known as 'outsider artists.' I think Charles Manson is probably the ultimate outsider: He is nowhere near our society or our reality."

Those close to Manson, 82, say he remains a committed environmentalist. "He has been completely consistent in speaking out against pollution since 1967, and is focused on saving our ATWA," the organization's CEO, Craig Hammond, says of his close friend. Manson founded ATWA, which claims to work with governments "to restore valuable ecological areas [and] to preserve all species of life on Earth." ATWA made $86 in 2015, according to a filing.

Hammond, whom Manson nicknamed Gray Wolf decades ago, tells Billboard that while Manson continues to create "beautiful melodies and powerful songs," he never writes them down. "It's just plain soul," he adds.

The catch: Manson cannot make money on his art while imprisoned in Corcoran. The California Department of Corrections and Rehabilitation restricts inmates from selling "written and artistic material," so Manson cannot recoup sales on Walking in the Truth or any other recordings available on sites like CharliesArts.com, which Wolf runs. Instead, proceeds help cover ATWA expenses.

In August 1969, Manson directed his so-called Family to murder those staying at the Los Angeles home he believed belonged to Melcher, the Beach Boys associate who had rejected him. The pregnant actress Sharon Tate was among the victims. Manson, 82, has been serving life sentences since 1971; he made news earlier this year when he was hospitalized.

Despite the stigma attached to collecting Manson's music, Tent says the vinyl release receives "overwhelmingly positive" reaction at record stores, where he's sold about 500 copies so far. "I think it's sort of a journey through his mind," Tent says, "rather than inside of prison walls."