The changing of one's voice is a male rite of passage. But most men go through it long before they turn 40. And the news doesn't usually land in the tabloids.

Chastity Bono became famous when, as a shy, towheaded toddler, she appeared on "The Sonny and Cher Comedy Hour," her parents' hit variety show. Four decades later, the former musician and gay and lesbian activist transitioned into Chaz, a man who - with a new book and documentary on OWN: Oprah Winfrey Network - looks poised to become the face of a still-nascent transgender movement.

"We were talking about how we were going to break the story, and it broke without us, because my voice started changing," Bono, 42, recently said of his transitioning process, achieved through surgery and hormone treatments. "People notice things and they call the tabloids.

"I couldn't do it privately," he continued. "So I could either have done it (and people would have known,) and other people would have written about it, and it wouldn't be the truth. Or I could do it myself and try to help people and put a face on an issue people don't understand."

"Becoming Chaz," the documentary that premieres tonight at 9 p.m. on OWN, details his breast-removal surgery, interactions with (mostly supportive) family members and relationship with his fiancee, Jenny. Interviews with his mother make it clear that Cher - one of the world's top entertainers - is still struggling with her son's decision, not to mention which pronouns to use in referring to him.

Winfrey, who last week taped a Bono interview for her syndicated show on Monday, is using the Chaz movie to launch a new documentary series on her cable network.

"The goal and intention is for Oprah to do for docs what she's done for books," said Fenton Bailey, who made the film with his longtime work partner Randy Barbato.

Meanwhile, the book "Transition: The Story of How I Became a Man," which Bono wrote with Billie Fitzpatrick, delves deeper into Bono's chaotic childhood after Cher split with Sonny Bono, the songwriter and singer who later became a successful Republican politician before dying in a skiing accident in 1998. Chaz - the couple's only child - recounts struggling with his identity even through childhood battles with his mother, including arguments about whether Chastity would wear a dress to school. (Cher's spokeswoman did not respond to an interview request.)

"It's probably the hardest I've worked on anything in my life," Bono said of the book.

"This journey wasn't just about transitioning; it was a journey of coming to understand myself, learning how to take care of myself, putting my fears away, and putting my needs as a priority instead of concerning myself with what everyone else thought," he continued. "It's, essentially, really about growing up."

Activists are already applauding Bono's moves. "There are few transgender storylines in entertainment media - television and movies," said Jarrett Barrios, president of the advocacy group GLAAD. "And even fewer where the story is told fully and fairly, so that the public understands why someone chooses to transition and what they're hoping for. ... Transgender people remain mostly invisible."

Though data are scarce, one commonly cited survey indicated that 0.2 percent of adults identify themselves as transgender. A UCLA study estimated that there are fewer than 700,000 transgender Americans. Transgender people frequently face discrimination in the workplace and elsewhere, Barrios said. "Here you've got a well-known celebrity who transitioned and who chose to open up his life to the world," Barrios said. "I think it's extraordinarily generous of Chaz."

Bono navigated some rough waters to get here. She came out as a lesbian in the 1990s. But a music career collapsed and other projects didn't pan out.

For some years she drifted through a fog of drug abuse - which she now interprets as her way of ignoring the identity problem that had gnawed at her for years. She identified in every way as a man but she had a woman's body.

"I thought that transgender people must have felt much worse than I did in order to risk losing all the things that one can lose by transitioning," Bono said.

"I think especially for parents there's a grieving process that has to happen," Bono said. "In a sense, that exact person doesn't exist anymore. But inside, the essence of me is still the same."