Like its slow-building title song, Isaac Hayes' Shaft soundtrack took a while to achieve its reputation as a symphonic-funk masterpiece.

He had broad access to the film's creative process, as director Gordon Parks passed along raw footage from the set for what at first was only a three-song assignment. MGM loved what they heard, and "Soulsville," "Ellie's Love Theme" and the title sequence, "Theme From 'Shaft,'" opened the door for a new contract to do the rest of the movie music.

This was no small thing. Parks was overseeing the first major studio production for a Black filmmaker, and he'd just tabbed an untested major recording artist with no film experience to compose both the songs and instrumental interludes.

Hayes wasn't one to back down from a challenge, even a historic one. "There's always hurdles. So I just keep moving, just constantly redefining myself," Hayes told NPR. "That's how you stay in the race."

MGM was playing something of a hunch, since it was coming off a successful pairing with then-unknown Earth, Wind & Fire on the low-budget indie film Sweet Sweetback's Baadasssss Song. They were met head on by Hayes' own outsize ambitions.

"I was Stax's No. 1 artist at the time," Hayes later remembered, "so I said, 'Okay, I'll give it a shot. I was excited just to do a movie score."

Parks' episodic approach gave Hayes plenty of entry points. He spent a couple of months, in between concert dates, completing the songs and then brought in longtime collaborators from Stax Records to set down the rhythm bed.

"My main concern at the beginning was not to get my head handed to me on a platter by Gordon Parks," Hayes told the New York Daily News in 2000. "He told me just to zero in on the character of Shaft – roving, relentless, always in pursuit."

Listen to Isaac Hayes' 'Theme From 'Shaft"

Hayes had a knack for taking fans into his characters' heads, but Parks had now given him permission to inhabit the role of the main protagonist himself. Hayes took on a thespian's gravitas among swelling strings, the hissing of a hi-hat and gurgling wah-wahs.

"He scores his records dramatically," celebrated industry figure Quincy Jones told DownBeat magazine in 1971. "He thinks theatrically."

Things began to move very quickly: Orchestral elements for the album were completed in one day; the vocals were done the next. But Hayes was never quite satisfied with the results, mainly because he was working on a more primitive three-track system at first. Ultimately, he'd rerecorded all of it back at Stax in Memphis before releasing Shaft in August 1971.

By then, the movie had already captured the imagination of moviegoers, earning millions and saving MGM from bankruptcy. Parks, a former Life magazine photographer, cast Richard Roundtree as the tough-talking, leather jacket-wearing, ladies-man detective. He became an instant star, as so-called "blaxploitation" action films were suddenly all the rage.

But Hayes' "Theme From 'Shaft,'" released just before the album, stood so far apart from what was on the radio at the time that it took a while for listeners to catch up. Everything from the velvety baritone vocals to its riffy sexuality feels definitive today for Hayes, for the film, for the wider blaxploitation genre. But, at the time, Hayes was breaking new ground in soul and funk.

"Cafe Regio's" and "No Name Bar" incorporated jazz influences, while "Ellie's Love Theme" was driven along by a lively vibraphone. In fact, the Shaft soundtrack was dotted with unusual instrumental elements – at least at the time. Today, it reads like a blueprint.

"He always wanted to incorporate flutes and strings, like Motown, and mixing the two was frowned upon by a lot of people on the Memphis music scene," Hayes' son Isaac III told Variety in 2021. "And if you fast forward to modern-day R&B, you can't imagine it without lush orchestrations, not just heavy bottom and bass. I would call my dad the inventor of modern R&B."

Ultimately, it took some three months for the title track to climb into the Top 10. The battles continued for Hayes. The soundtrack LP followed "Theme From 'Shaft'" to the top of the chart, and he went on to several Grammy nominations – including Album of the Year. An Oscar nod was a far more remote possibility, however, since Hayes wasn't a composer in the proper sense of the word. He couldn't even annotate his own music, as some critics loudly noted.

Listen to Isaac Hayes' 'Ellie's Love Theme'

"Hollywood tried to shut me out," Hayes lamented years later. "It took some guys to allow me to be nominated: Quincy Jones, J.J. Johnson, Henry Mancini and Dominic Frontiere fought for me to get that nomination." Hayes ultimately claimed the Academy Award for "Theme From 'Shaft,'" a defining moment for popular musicians with hopes to break into the movie industry. "It put me in another league," Hayes acknowledged to Jon Burlingame in 2005. "I was an R&B artist, doing my thing, and then I started scoring movies. It was a blessing in disguise."

Then just 29 years old, Hayes was also the first Black musician to win an Oscar for his song, opening the door for generations to follow. Curtis Mayfield was suddenly composing Super Fly, and Marvin Gaye was working on Trouble Man. In some cases, the music from subsequent blaxploitation films became more famous than anything ever shown onscreen. "It was the achievement of his life," Isaac Hayes III told Variety, "coming from poverty the way that he did, and the struggles that he had. Shaft was something otherworldly for a kid from Memphis, Tenn., that picked cotton, worked in a hog factory and got all the way to the Academy Awards. As a Black man, in 1971, it was incredible."

He followed Shaft with the Top 10 smash Black Moses later in 1971 but never again reached the top of the pop charts. Hayes' next two albums (1973's Joy and 1975's Chocolate Chip) were gold sellers, but they barely squeaked into the Top 20. After that, he never got higher than the 1979's No. 39 hit Don't Let Go. Hayes took it all in stride, rebuilding his career several times after divorce and bankruptcy. "If you cherish the fragrance of a rose," Hayes told the San Francisco Gate in 1975, "you must accept the thorns." (Hayes died in 2008.)

Shaft provided a wellspring of cultural relevance and cash revenue over the years, even as the title track eclipsed much of Hayes' other worthy achievements. It's been covered and sampled, morphed into disco songs and remixes, and powered new soundtracks, commercials and political campaigns. A 2000 remake of the film by John Singleton opened with Hayes' "Theme From 'Shaft'" before making way for more contemporary figures like R. Kelly and Heavy D.

By then, Hayes had come to terms with his biggest hit. "I'm kind of removed from it now," Hayes told Entertainment Weekly in 1995. "I can finally enjoy 'Shaft.' In fact, I listened to it two days ago and said, 'Damn, that's fresh!'"

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