US singer-songwriter Isaac Hayes has died at his home in Memphis, Tennessee, at the age of 65.
Police were called after his wife found him unconscious next to a moving treadmill. He was taken to hospital, where he was pronounced dead.
Hayes, a flamboyant, deep-voiced performer, won an Oscar for the 1971 hit Theme From Shaft.
He was perhaps better known to a younger audience as the voice of Chef from the hit cartoon show, South Park.
The cause of death was not immediately known.
"Family members believe at this point it is a medical condition that might have led to his death," a police spokesman said, adding Hayes was being treated for "a number of medical issues".
Hayes suffered a stroke in 2006.
But he was about to begin work on a new album for Stax, the soul record label he helped build to legendary status.
British soul star Jazzie B, who became friends with Hayes after they performed together in the 1990s, described him as "a really nice man" and "as cool as ice".
"He was an equal cornerstone to the evolution of hip-hop, what's come to be known as R&B, and urban music in general," he told BBC News.
"So there's absolutely no doubt that Isaac Hayes will be truly missed and he was a very influential part of music as we hear it today."
Collin Stanback from the Stax label told the Associated Press news agency that the star "embodies everything that's soul music".
He added: "When you think of soul music, you think of Isaac Hayes - the expression, the sound and the creativity that goes along with it."
Hayes - along with Al Green, James Brown and Stevie Wonder - was one of the dominant black artists of the early 1970s.
The star, a self-taught musician, was hired in 1964 by Stax Records as a pianist and saxophonist, working as a session musician for big names such as Otis Redding.
He established a songwriting partnership with David Porter, and in the 1960s, writing hits for Sam and Dave such as Hold On, I'm Coming and Soul Man.
This success led to a recording contract, and in 1969 he shot to fame with the release of the groundbreaking album Hot Buttered Soul.
In 2002 Hayes was inducted into the Rock and Roll Hall of Fame
The theme from the film Shaft was a number one hit in 1971. 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.
In a statement released from The Recording Academy, the body behind the Grammys, president Neil Portnow called him a "true renaissance man".
He added: "After laying the groundwork for the Memphis soul sound through his work with Stax Records, his groundbreaking theme song and score for the movie Shaft cemented his status as a musical icon.
"The world has lost a true creative genius and a passionate humanitarian, but his indelible legacy will remain ever present.
"Our deepest sympathies go out to his family, friends and all who were inspired by the man and his music," added Mr Portnow.
When he was elected to the Rock and Roll Hall of Fame in 2002, he put his success down to good chance.
"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."
Hayes was also in several movies, including It Could Happen to You with Nicolas Cage, and Ninth Street with Martin Sheen.
He achieved a different of popularity later in life as the voice of the South Park character, Chef. But he angrily quit the show in 2006 after an episode mocked Scientology, a religious movement to which he belonged.
He was married four times and has 12 children.
Your comments and memories:
I met Issac Hayes very briefly, backstage after his set at the Womad festival in 2007. A year of mud and muck. Trying to get a brief word from him for the radio, we held the mic out and asked what he thought of the festival. The legendary voice came back with: "It's wet, but it's wild." Worth all the muck and rain just for that remark. Radio shows across the world will be playing his tracks for the next couple of weeks. He'll be sadly missed. Rory McSwiggan, Brent, London
I had the pleasure of meeting Isaac when I worked with him on Soul Survivors filmed in Liverpool for BBC TV. I am also a musician and Isaac came to see me play at a local gig and invited me to play at House of Blues. Unfortunately, I never had the opportunity but did repay the compliment by going to HIS gig at the Albert Hall!! He was a real gentleman and will be missed by many.Ozzie Yue, Liverpool, UK
My wife and I saw Isaac perform last year in New York and he was awesome, just as he was back in the day. What a terrible loss to the would of Soul Music. I'm sure he knew just how much of an ICON of the 70s he truly was. Colin, New York, NY
Isaac Hayes was an astonishing and incredibly appealing musician, who won fans across the board. His music was accomplished to the degree that even listeners who ordinarily weren't fans of soul would find something to appreciate in his songs. He was a genuine rare talent - a musical genius - and he will be fondly remembered by millions. Matt O'Leary, Siena, Italy
I'm a little younger then a lot of his fans, but I did know some of his music and I did enjoy it. He will be missed! We love you Isaac Hayes and you will always be remembered. Danielle Pinkeny, Temple Hills USA
I can't believe it. I saw him at Glastonbury in 2003 and he was so good. I first got into him through Shaft and then discovered Hot Buttered Soul. His voice, like his song writing was a force of nature. His soul will live on. Clark, London
Another of the Soul/Funk greats gone. He will be missed but live on in his music. I dig it, brother. Ozzy, Cambridge, UK
This truly is a death of a legend. I'll never forget his performance at the Glastonbury festival in 2002, it was a truly fantastic performance, and he left me with a Cheshire Cat-style grin for the rest of the day. Very sad to read this news. John, Bath, England
I remember this illustrious son of Afro-American when he had a joint musical show with the late Fela Anikulapo-Kuti in Lagos, Nigeria. It was a beautiful concert seeing two well-talented music gurus at their best. Adieu Isaac Hayes. Francis Ayodeji, York, UK
As a lifelong fan of South Park, I am dismayed to hear of Isaac Hayes's untimely death. Chef was my favourite character in many an episode and his presence will be deeply missed by myself and many others. I am pleased to hear that he had a good, productive life and leaves many children behind to continue his heritage, so in a way this serves as a celebration. But still, 65 is too young. R.I.P. Toby Corke, Brighton, England
Brilliant man. The spooky thing is if you visit his official website here: http://www.isaachayes.com/myframes.html - there is a picture of him and Bernie mac who died yesterday. God bless the soul men. Sean, E Yorks