Gold died Friday in his sleep at his home in Encino, said his sister, Melani Gold Friedman. He had cancer but had been responding well to treatment, she said.
"Andrew was so enormously talented it almost seemed effortless," Ronstadt told The Times on Saturday. "He was a real cornerstone of those early records."
He met Ronstadt as a high school student in the 1960s when her country-rock band the Stone Poneys performed at Oakwood School in North Hollywood. "He came up to talk," Ronstadt said. "He was so bubbly and so smart and we were so impressed with what a good musician he was."
After the Stone Poneys disbanded after their hit "Different Drum" in 1967, founding member Kenny Edwards teamed with Gold and singer-songwriters Wendy Waldman and Karla Bonoff to create the folk-rock band Bryndle.
In an email to The Times, Gold's former high school classmate Waldman called him "an extraordinary guitarist, pianist, drummer and record producer."
Bryndle got a record deal, but the album wasn't released. The band broke up (but reunited in the 1990s). Edwards, who died in August, rejoined Ronstadt and Gold joined the band.
Gold was born Aug. 2, 1951, in Burbank to composer Ernest Gold and singer Marni Nixon. His father won an Academy Award for his score for the 1960 film "Exodus," and his mother sang for Natalie Wood in "West Side Story" and Audrey Hepburn in "My Fair Lady," among others.
"It was clear from the beginning that I was going to be a musician," he told The Times in 1977. "With those kind of influences at home what else could I do?"
Gold's sister said he taught himself instruments by listening to the Beatles. "He could really pick up any instrument and play it," she said. He lived in England with family friends for about a year as a teenager, she said, and recorded a single with another young musician.
Waldman said Gold "listened to everything under the sun and absorbed it with terrifying accuracy. It was something I always admired and found fascinating about him."
Gold launched a solo career in the mid-1970s while still with Ronstadt's band. "Lonely Boy" was a hit on his second album, "What's Wrong With This Picture?" and the single "Thank You for Being a Friend" from 1978's "All This and Heaven Too" reached No. 25 on Billboard magazine's charts.
He recorded with English musician Graham Gouldman in the 1980s, then continued to write, record and work with a variety of artists. Gold also did commercial work and soundtracks, such as singing the theme to the NBC sitcom "Mad About You." His last release was 2008's "Copy Cat."
In addition to his sister, who lives in Tujunga, and his mother, Gold is survived by his wife, Leslie Kogan; daughters Emily, Victoria and Olivia from his marriage to Vanessa Gold, which ended in divorce; and sister Martha Carr of North Hollywood.
Services will be private, but a public remembrance will be planned.
Los Angeles Times staff writer Randy Lewis contributed to this report.