MEMPHIS, Tenn.. -- Isaac Hayes, pioneering songwriter and Grammy-winner for "Theme From Shaft," died Sunday at age 65.

The Shelby County Sheriff's Office said a family member found Hayes unresponsive near a treadmill on Sunday. He was pronounced dead about an hour later at Baptist East Hospital in Memphis. 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 official Isaac Hayes Web site said that Hayes moved back to Memphis in 2003 and took off on the Chef theme, opening restaurants and a cooking store.

The Rev. Al Sharpton, president of National Action Network, released a statement Sunday about the death.

"I am deeply saddened by the loss of Isaac Hayes, a true historic world music figure. Isaac Hayes was the first African-American to win an Oscar for a music score but never lost sight of his commitment to his community and the betterment of mankind. He was more than an artist he was a trailblazer, He was an innovator. He was a creative genius. I shall never forget how in the height of his career he still had time to work and lend his celebrity to those of us much younger and at that time who were totally unknown. Even in his later years he never hesitated to appear for a cause or endorse something that he felt was for the good of mankind. He will be sorely missed."

In Riverside, Calif., Hayes will be honored as planned on the final day of the Inland Empire Jazz Festival on Aug. 24, the event's executive director said Sunday.

Annetta Bryant, speaking Sunday afternoon from Rancho Cucamonga, said she did not have a statement to make about Hayes' untimely death.

But Bryant confirmed the festival's plans to go ahead with plans to honor Hayes and the Isaac Hayes Foundation, which promotes human rights worldwide.

Hayes was expected to attend and become the first recipient of the festival's "Celebrate Life Award."