Linda Ronstadt's new memoir, titled "Simple Dreams," is a rocket ride through a megahit career and the glory days of rock and roll.

It makes no mention, however, of her battle with Parkinson's disease, which she disclosed to AARP in August. Ronstadt said, at the time, she was still finishing up the book and a diagnosis had not been officially confirmed.

"It was so great to think that there was a chance that I didn't have it," she said. "I was kind of glorying in that reality for a while, you know? But I do and that's just that."

(ABC News)

Linda Ronstadt, Michael J. Fox Soften 'Cruel' Hand of Parkinson's Disease

Ronstadt was born in Arizona. At 4 years old, she already had the voice that would earn her 12 Grammys. She was the first woman ever to have four platinum albums in a row. In the golden age of rock, everyone from Johnny Cash and Jackson Browne to Kermit the Frog wanted to sing with her.

But Ronstadt said that for perhaps 12 to 15 years, she likely suffered unknowingly from the disease.

"I was struggling to sing for so many years," she said. "I knew there was something dramatically, systemically wrong. And I knew it was mechanical and it was muscular. … I had no control over the muscular, you know. … The brain has to be able to send very, very subtle cues to your vocal chords and get the muscles to vibrate a certain way."

She said that, at some point, she couldn't even make the notes.

"I'd aim for a C and I'd hit a G," Ronstadt said. "It's like my elevator would go to the wrong floor all the time."

She sang publicly for the last time in 2009.

Even as she suffered through extreme physical exhaustion - she said it was hard to comb her hair, brush her teeth - Ronstadt said Parkinson's was the last thing she'd suspected, even though her grandmother had suffered from the disease.

It wasn't until she began to get the classic tremor in her hands that a doctor made the diagnosis. Ronstadt said it was then that the floor gave way under her feet.

"Yeah, there was a real, kind of 'holy s-t' moment,'" Ronstadt said. "You sort of go, 'Yow. This has happened.'"

Today, she lives a life full of reading and loving other people's music.

"When I wake up in the morning, I think, 'I can walk and I can talk, so it's a good day,' you know," she said. "'Cause there'll probably come a day when I can't do those things."

ABC News' Margaret Dawson contributed to this story.