A family member found Hayes unresponsive near a treadmill and he was pronounced dead about an hour later at Baptist East Hospital in Memphis, according to the sheriff's office. The cause of death was not immediately known.
In the early 1970s, Hayes laid the groundwork for disco, for what became known as urban-contemporary music and for romantic crooners like Barry White. And he was rapping before there was rap.
His career hit another high in 1997 when he became the voice of Chef, the sensible school cook and devoted ladies man on the animated TV show "South Park."
The album "Hot Buttered Soul" made Hayes a star in 1969. His shaven head, gold chains and sunglasses gave him a compelling visual image.
"Hot Buttered Soul" was groundbreaking in several ways: He sang in a "cool" style unlike the usual histrionics of big-time soul singers. He prefaced the song with "raps," and the numbers ran longer than three minutes with lush arrangements.
"Jocks would play it at night," Hayes recalled in a 1999 Associated Press interview. "They could go to the bathroom, they could get a sandwich, or whatever."
Next came "Theme From Shaft," a No. 1 hit in 1971 from the film "Shaft" starring Richard Roundtree.
"That was like the shot heard round the world," Hayes said in the 1999 interview.
At the Oscar ceremony in 1972, Hayes performed the song wearing an eye-popping amount of gold and received a standing ovation. TV Guide later chose it as No. 18 in its list of television's 25 most memorable moments. He won an Academy Award for the song and was nominated for another one for the score. The song and score also won him two Grammys.
"The rappers have gone in and created a lot of hit music based upon my influence," he said. "And they'll tell you if you ask."
Hayes was elected to the Rock and Roll Hall of Fame in 2002.
"I knew nothing about the business, or trends and things like that," he said. "I think it was a matter of timing. I didn't know what was unfolding."
A self-taught musician, he was hired in 1964 by Stax Records of Memphis as a backup pianist, working as a session musician for Otis Redding and others. He also played saxophone.
He began writing songs, establishing a songwriting partnership with David Porter, and in the 1960s they wrote such hits for Sam and Dave as "Hold On, I'm Coming" and "Soul Man."
All this led to his recording contract.
In 1972, he won another Grammy for his album "Black Moses" and earned a nickname he reluctantly embraced. Hayes composed film scores for "Tough Guys" and "Truck Turner" besides "Shaft." He also did the song "Two Cool Guys" on the "Beavis and Butt-Head Do America" movie soundtrack in 1996.
Additionally, he was the voice of Nickelodeon's "Nick at Nite" and had radio shows in New York City (1996 to 2002) and then in Memphis.
He was in several movies, including "It Could Happen to You" with Nicolas Cage, "Ninth Street" with Martin Sheen, "Reindeer Games" starring Ben Affleck and the blaxploitation parody "I'm Gonna Git You, Sucka."
In the 1999 interview, Hayes described the South Park cook as "a person that speaks his mind; he's sensitive enough to care for children; he's wise enough to not be put into the 'whack' category like everybody else in town - and he l-o-o-o-o-ves the ladies."
But Hayes angrily quit the show in 2006 after an episode mocked his Scientology religion. "There is a place in this world for satire, but there is a time when satire ends and intolerance and bigotry towards religious beliefs of others begins," he said.
Co-creator creators Matt Stone responded that Hayes "has no problem - and he's cashed plenty of checks - with our show making fun of Christians." A subsequent episode of the show seemingly killed off the Chef character.
Hayes was born in 1942 in a tin shack in Covington, Tenn., about 40 miles north of Memphis. He was raised by his maternal grandparents after his mother died and his father took off when he was 1½. The family moved to Memphis when he was 6.
Hayes wanted to be a doctor, but got redirected when he won a talent contest in ninth grade by singing Nat King Cole's "Looking Back."
He held down various low-paying jobs, including shining shoes on the legendary Beale Street in Memphis. He also played gigs in rural Southern juke joints where at times he had to hit the floor because someone began shooting.