He was born Howard Andrew Williams in Wall Lake, Iowa, on Dec. 3, 1927. In his memoir, Williams remembered himself as a shy boy who concealed his insecurity "behind a veneer of cheek and self-confidence."
Williams began performing with his older brothers Dick, Bob and Don in the local Presbyterian church choir. Their father, postal worker and insurance man Jay Emerson Williams, was the choirmaster and the force behind his children's career.
When Andy was 8, Williams' father arranged for the kids to have an audition on Des Moines radio station WHO's Iowa Barn Dance. They were initially turned down, but Jay Emerson Williams and the young quartet kept returning, and they were finally accepted. The show attracted attention from Chicago, Cincinnati and Hollywood. Another star at WHO was a young sportscaster named Ronald Reagan, who would later praise Williams as a "national treasure."
The brothers joined Bing Crosby in recording the hit "Swinging on a Star" in 1944 for Crosby's film "Going My Way," and Andy, barely a teenager, was picked to dub Lauren Bacall's voice on a song for the film "To Have and Have Not." His voice stayed in the film until the preview, when it was cut because it didn't sound like Bacall's.
Later the brothers worked with Kay Thompson of eventual "Eloise" fame, then a singer who had taken a position as vocal coach at MGM studios, working with Judy Garland, June Allyson and others. After three months of training, Thompson and the Williams Brothers broke in their show at the El Rancho Room in Las Vegas to a huge ovation. They drew rave reviews in New York, Los Angeles and across the nation, earning a peak of $25,000 a week.
Williams, analyzing their success, once said: "Somehow we managed to work up and sustain an almost unbearable pitch of speed and rhythm."
After five years, the three older brothers, who were starting their own families, had tired of the constant travel and left to pursue other careers.
Williams initially struggled as a solo act and was so broke at one point that he resorted to eating food intended for his two dogs.
"I had no money for food, so I ate it," he recalled in 2001, "and it actually was damned good."
A two-year TV stint on Steve Allen's "Tonight Show" and a contract with Cadence Records turned things around. Williams later formed his own label, Barnaby Records, which released music by the Everly Brothers, Ray Stevens and Jimmy Buffett.
Williams was a lifelong Republican who once accused President Obama of "following Marxist theory." But he acknowledged experimenting with LSD, opposed the Nixon administration's efforts in the 1970s to deport John Lennon and in 1968 was an energetic supporter of Robert Kennedy's presidential campaign. When Kennedy was assassinated in Los Angeles in June 1968, just after winning the California Democratic primary, Williams sang "The Battle Hymn of the Republic" at his funeral.
"We chose that song because he used it on the campaign trail," Williams later said of Kennedy, who had been a close friend. "He had a terrible voice, but he loved to sing that song. The only way I got through singing in church that day was by saying, `This is my job. I can't let emotion get in the way of the song.' I really concentrated on not thinking about him."
After leaving TV, Williams headed back on the road, where his many Christmas shows and albums made him a huge draw during the holidays. One year in Des Moines, however, a snowstorm kept the customers away, and the band's equipment failed to reach Chicago in time for the next night's show. The musicians had to borrow instruments from a high school band.
"No more tours," Williams decreed.
He decided to settle in Branson, with its dozens of theaters featuring live music, comedy and magic acts, and was among the first wave of national entertainers to perform there regularly.
When he arrived in 1992, the town was dominated by country music performers, but Williams changed that, building his classy, $13 million theater in the heart of the entertainment district and performing two shows a night, six days a week, nine months of the year. Only in recent years did he begin to cut back to one show a night.
Not surprisingly, his most popular time of the year was Christmas, although he acknowledged that not everyone in Hollywood accepted his move to the Midwest.
"The fact is most of my friends in L.A. still think I'm nuts for coming here," he told The Associated Press in 1998.
He and his second wife, the former Debbie Haas, divided their time between homes in Branson and Palm Springs, where he spent his leisure hours on the golf course when Branson's theaters were dark during the winter months following Christmas.
Retirement was not on his schedule. As he told the AP in 2001: "I'll keep going until I get to the point where I can't get out on stage."
Williams is survived by his wife, Debbie, and his three children, Robert, Noelle and Christian.