Bob Johnston, 83, a musical maverick who produced career-changing albums for leading folk and country artists of the 1960s and '70s, including "Blonde on Blonde" for Bob Dylan and "At Folsom Prison" for Johnny Cash, has died.

The veteran producer, who also guided Simon & Garfunkel's "Sounds of Silence" and Leonard Cohen's "Songs of Love and Hate," died of heart failure Friday in Gallatin, Texas, said his son, Kevin.

Johnston, a producer for Columbia Records in New York in the 1960s, was known as a fierce advocate for creative freedom. He defied Columbia executives who opposed Cash's idea of performing at Folsom and San Quentin; the Folsom album became a huge hit and helped revive the singer's career. In "Blonde on Blonde" — considered a landmark in American popular music — he allowed a single song, "Sad-Eyed Lady of the Lowlands," to run for 11 minutes.

Johnston also literally tore down walls on his artists' behalf: At Columbia's Nashville studios, he infuriated studio managers by removing the baffles that prevented sound leakage but also stifled interplay among the musicians. Dylan wanted all the musicians playing with him to be able to see one another.

To ensure that no mechanical failures would interrupt the flow, Johnston also insisted that studio engineers keep two or three tape machines running during sessions.

"His idea for producing a record was to keep the machines oiled, turn 'em on and let 'er rip," Dylan, who described his collaborations with Johnston as "a drunken joyride," wrote in his memoir "Chronicles: Volume One," in 2004.

Unlike legendary producers Phil Spector and Sam Phillips, Johnston was not known for creating his own unique sound or discovering talent, "but any fan of country, rock and folk music from the 1960s probably has a record Bob Johnston produced," said Michael Gray, who curated "Dylan, Cash, and the Nashville Cats," an exhibit at the Country Music Hall of Fame and Museum in Nashville.

"He matched musicians with the artist, kept the tapes rolling and captured everything."

Johnston was born in Hills­boro, Texas, on May 14, 1932, and grew up in Fort Worth. His mother, Diane Johnston, was a songwriter who wrote for Gene Autry, Roy Rogers and Eddy Arnold. His father, Jay, was a chiropractor.

After serving in the Navy in the early 1950s, Johnston began composing. He later moved to New York and recorded under the name Bobby Johnston, turning out a minor hit with a Del Vikings song, "Flat Tire."

Johnston also wrote songs for Elvis Presley in collaboration with his wife, Joy Byers, and others, including Charlie Daniels.

Besides his wife and son, he is survived by three grandchildren.

Dr. James "Red" Duke Jr., Houston's iconic cowboy-style doctor who delivered homespun health advice on nationally syndicated television programs and founded the city's helicopter ambulance system Life Flight, died Tuesday. He was 86.

Duke, a trauma surgeon who attended to Texas Gov. John Connally the day of President John F. Kennedy's assassination in Dallas, succumbed to natural causes at Memorial Hermann Hospital in the Texas Medical Center. He had been in declining health for the past year.

"Red was a true pioneer in medicine for our community — a visionary in trauma care, a dedicated doctor, a superb educator, the larger-than-life figure that everyone knew," said Dan Wolterman, president of Memorial Hermann Health System, where Duke practiced for four decades.

"He was everyone's friend."