Miller, who accompanied Sinatra from 1951 until the legendary singer's final performance in 1995, died Tuesday from complications of a heart attack, The Los Angeles Times reported.
Miller had been performing in Montreal with Frank Sinatra Jr. when he broke his hip two weeks ago, and then suffered a heart attack. He died after heart bypass surgery, his daughter, Meredith, told the Times.
Miller had been playing 14 songs a night in Sinatra Jr.'s show, including "One for My Baby (and One More for the Road)," the saloon song he introduced to the elder Sinatra in the early 1950s -- and which he played at the late singer's funeral in 1998.
"Bill Miller was the greatest accompanist that any popular singer ever had," Sinatra Jr. told the newspaper.
Miller was born in Brooklyn, N.Y. Largely self-taught at the piano, he began playing professionally when he was 16.