MEMPHIS, Tenn. - Isaac Hayes, the pioneering singer, songwriter and musician whose relentless "Theme From Shaft" won Academy and Grammy awards, died Sunday afternoon, the Shelby County Sheriff's Office said. He was 65.

A family member found him unresponsive near a treadmill and he was pronounced dead 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."

Steve Shular, a spokesman for the sheriff's office, said authorities received a 911 call after Hayes' wife and young son and his wife's cousin returned home from the grocery store and found him collapsed in a downstairs bedroom. A sheriff's deputy administered CPR until paramedics arrived.

"The treadmill was running but he was unresponsive lying on the floor," Shular said.