Isaac Hayes, who penned songs that would provide the backbone of Memphis soul and as a performer reached millions through his award-winning “Theme From Shaft,” was found dead at his home in Memphis on Sunday. He was 65, just a week shy of his next birthday.

The Associated Press reported that a family member found Hayes unresponsive near a treadmill, according to the Shelby County Sheriff’s Office report. He was pronounced dead about an hour later at Baptist East Hospital in Memphis. The cause of death was not immediately known.

Hayes denied rumors that he suffered a stroke in early 2006, although he had been hospitalized for treatment of high blood pressure. He was well enough to make appearances in 2006 and ’07 in conjunction with the 50th anniversary of the founding of Stax Records, the Southern soul label where he was an inhouse songwriter and producer in the 1960s.

From the mid-’60s through the mid-’70s, few artists had as great an impact on black American music as Hayes: He wrote era-defining hits such as “Soul Man” and “Hold on, I’m Comin’”; he was an active session keyboardist; his solo albums were the biggest-sellers in Stax’s history; and his score for “Shaft,” which won two Grammys and the Oscar for song, opened the doors for black songwriters in Hollywood.

Born in Covington, Tenn., in 1942, his first session at Stax was as a baritone saxophonist in 1963. Stax owner Jim Stewart hired Hayes to fill in on keyboards for Booker T. Jones, who was away at college.

A husky baritone, Hayes had been reluctant to move out front as a headliner, but an odd business deal in 1969 required several of Stax session musicians to make solo albums as the label generated 27 albums simultaneously to make up for the back catalog that was sold to Atlantic Records.

“Hot-Buttered Soul” was Hayes’ work. Radical for its day, it only included four songs, among them an 18-minute version of “By the Time I Get to Phoenix” and a 12-minute “Walk on By,” lengths that had not been explored in R&B.

According to Rob Bowman’s liner notes to “Ultimate Isaac Hayes: Can You Dig It?,” the album received airplay in Detroit and was so popular that record shops in the Motor City were burglarized and the only thing missing would be copies of “Hot Buttered Soul.” The album had a unique success, reaching high on four different charts — jazz, pop, R&B and easy listening. Two years after its release, it was still in the jazz top 10, along with two of Hayes’ other albums.

On the heels of that success, Hayes was commissioned to write the score for one of the first blaxploitation films, Gordon Parks’ “Shaft.” Two of the theme’s sonic signatures came from two abandoned ideas: Hayes had tried to use the hi-hat sound on Otis Redding’s “Try a Little Tenderness” and the wah-wah part was a riff Hayes and Charles “Skip” Pitts had recorded and discarded.

The “Shaft” album went to No. 1 on pop and R&B charts and remained on the pop charts for 14 months. The single hit No. 1 pop and No. 2 R&B.

Within a couple of years, Curtis Mayfield, Marvin Gaye, Bobby Womack, James Brown and other black stars had been tapped to compose and record for film.

Bald and bearded, Hayes was an imposing figure and his appearance onstage in chains only added to his mystique. He earned the nickname Black Moses, which he would use as the title to his follow-up to “Shaft.”

Stax’s financial problems led the label to cut ties with Hayes, who then signed with ABC Records, which created the Hot Buttered Soul label for him. Between 1975 and 1977, he released five albums and had some minor R&B hits.

He recorded only once in the 1980s and made a pair of albums in 1995, putting more effort into developing an acting career.

He appeared in the films “Escape From New York,” “I’m Gonna Git You Sucka,” “Hustle & Flow,” “Robin Hood: Men in Tights” and “Johnny Mnemonic.”

On TV, he appeared in “The A-Team,” “Miami Vice” and “The Rockford Files,” but he was best known as the voice of school cafeteria cook and ladies’ man Chef on the animated “South Park.” He left the show in late 2005 after the program attacked Scientology, the religious movement of which he was a member.

Hayes was inducted into the Rock and Roll Hall of Fame in 2002.

He was married four times and has 12 children.