In a 1962 radio interview, the famed R&B disc jockey Magnificent Montague once asked Sam Cooke to define soul music in eight bars. Cooke’s response — a wordless hum that curved gently around an imagined melody with inexplicable poignancy — was so spot-on that it could have been transcribed as sheet music in dictionaries in lieu of a traditional written definition. It was a decade later when Bill Withers, who died today at the age of 81, did him one better, offering an unmistakable summary of soul music in a single bar, instead of eight. Cue up “Grandma’s Hands,” right before the first verse starts, and you’ll know it when you hear it: “mmm-hmmm…”

“Grandma’s Hands” was the song that convinced Clarence Avant, owner of then nascent Sussex Records, to sign Withers to his first contract in the early 1970s. A West Virginia native who wound up working at a Los Angeles airplane parts factory after a stint in the Navy, Withers had unsuccessfully shopped his self-made demo to labels all over town, but Avant saw something special in that song. When I asked him what that “something” was during an interview a few years ago, Avant squinted at me as though I’d just posed the most absurd question imaginable, and replied: “Hell, everybody’s got a grandma.”

But that was only part of it. The song is a perfect encapsulation of Withers’ lyrical gifts — a Proustian lullaby that achieves universality through an accumulation of hyper-specific autobiographical details — but it’s that wordless throat-clearing at the beginning that serves as the first bite of the madeleine. You can see a similar magic at work in Withers’ other early hit, “Ain’t No Sunshine,” in which his placeholder lyrics for a never-written second verse — the phrase “I know” repeated 26 times — convey depths of longing and regret that no words could have properly plumbed. Like all of the greatest soul singers, Withers knew that soul defies language.

Of course, Withers was more than just a soul singer, at least in the early-’60s sense of the term. His style could reach further back, to the primal power of the early bluesmen, and further forward, to the smoother sounds of the Laurel Canyon folkies like Stephen Stills, who played guitar on Withers’ debut. (And perhaps even further forward than that: Blackstreet’s “No Diggity,” one of the most ubiquitous R&B hits of the 1990s, was built on a sample of that one bar from “Grandma’s Hands.”) Ultimately, although you can track clear traces of Withers’ influence on everyone from D’Angelo to John Legend and Fiona Apple, his style was entirely his own.

In his late twenties before he ever picked up a guitar, and well into his thirties before he ever had an album released, Withers was a classic late bloomer, yet he had the good fortune to break big just as black popular music was entering a period of relative liberation — its artists increasingly uninterested in watering down their material to appeal to white audiences. Motown stars like Marvin Gaye and Stevie Wonder were just beginning to break away from the rigid constraints of that label-machine and become full-fledged musical auteurs. Funkadelic and Sly Stone were combining R&B with rock and psychedelia in ways that permanently expanded the scope of black music. And previously behind-the-scenes craftsmen like Quincy Jones and Isaac Hayes had become household names as both solo stars and film music composers.

Even within that company, however, Withers was an anomaly: a pop star thoroughly in the black music tradition, but one whose songs demanded he be allowed the same sort of room for introspection, intimacy and first-person earnestness that tended to only be granted to white singer-songwriters. Resolutely unflashy and uninterested in following trends, Withers’ music was ever warm and comforting, but rarely as straightforward as it seemed. “Who Is He (And What Is He to You)” — perhaps the most seamless coupling of folk and funk ever put to record — is a somewhat lurid wronged-man track at heart, but Withers’ cheeky asides (“When I add the sum of you and me / I get confused and keep coming up with three”) and that “dadgummit!” dropped into the chorus give it an almost wholesome charm. “I Can’t Write Left-Handed” is unambiguous in its anti-Vietnam stance, and yet as a story-song it elides its most devastating detail with a deftness worthy of Flannery O’Connor. But he also knew when to leave well enough alone, and his most enduring composition, “Lean on Me,” is all the more powerful for its unabashed, unhedged tenderness.

Even as the grist in his music was smoothed out in his post-Sussex years, Withers was never slick, and he never lost his blue-collar humility. (Questlove recently called Withers “the closest thing black people have to a Bruce Springsteen,” although perhaps that’s a bit backwards, as Withers actually lived the nine-to-five lunch-pail lifestyle that The Boss only embraced in song.) It was probably an outgrowth of that everyman perspective that led him to leave music altogether in the 1980s, rather than continue to doggedly chase success with unsympathetic new label bosses and a polished, MTV-mode of stardom on the rise. It certainly wasn’t as though his songs had gone out of style — Club Nouveau had a No. 1 hit with a cover of “Lean on Me” just two years after Withers stopped recording.

Perhaps the secret of Bill Withers was that he approached music with a workingman’s sense of purpose, but never a careerist’s desperation. “I don’t know if I’m built to be the center of attention all the time,” he told the Washington Post a decade ago. “I’ve been fortunate enough that the music that I’ve done seems to have its own life without me having to show up everywhere and wave.” Like all great soul singers, he knew when the melody alone was enough.