When B. B. King took the stage at the Harlem Cultural Festival in the summer of 1969, the M.C. introduced him as “the world’s greatest blues singer,” a moment captured in the recent Questlove documentary, Summer of Soul. That was how much of the Black community regarded Riley “B. B.” King, from his ascent to the top of the R&B charts in the 1950s until well after his embrace by younger white musicians and fans in the late 1960s: as a great singer, first and foremost.

White fans, by contrast, recognized King primarily as a guitarist, one of the greatest ever to bend a string. In my new biography of B. B. King, King of the Blues, I argue that he almost singlehandedly codified and popularized a lyrical style of solo guitar that would suffuse popular music until the end of the 20th century and beyond.

For years after his recorded debut, in 1949, the Mississippi-born musician played like no one else, synthesizing the styles of R&B giants Lonnie Johnson and T-Bone Walker and jazzman Charlie Christian into one all his own. In the mid-60s, King’s sound spread to Britain, passing to Eric Clapton, Jeff Beck, and Jimmy Page, and then to Fleetwood Mac’s Peter Green, Pink Floyd’s David Gilmour, and a transplanted American who would outpace them all, Jimi Hendrix.

Toward the end of the 1960s, King crossed over from Black to white audiences, releasing a string of eclectic blues-rock-funk LPs, touring with the Rolling Stones, and scoring a major national hit at the decade’s close with “The Thrill Is Gone.”

B. B. King played like no one else, synthesizing the styles of R&B giants Lonnie Johnson and T-Bone Walker and jazzman Charlie Christian into one all his own.

White fans and the rock-music press focused obsessively on King’s guitar craft, which had launched an army of guitar heroes. But King continued to play for his aging Black audience, a constituency that still knew him as a chart-topping blues singer. While researching stacks of clippings about King in the Black press of the 1950s, I found precious few that even mentioned his guitar. “Lucille,” King’s legendary guitar, was not named in print until 1967.

Black fans celebrated King as a singer and bandleader because the R&B industry of the 1950s had no category for celebrated guitarists. The guitar remained a backbench instrument. Not for another decade would the guitar hero emerge, an archetype King largely inspired, along with Chuck Berry and a few other stylistic pioneers.

“Lucille,” King’s legendary guitar, was not named in print until 1967.

Thus, when King stepped out onto the stage at the Regal Theater in Chicago on November 21, 1964, for a performance that would yield perhaps the most famous album of guitar blues, Live at the Regal, the M.C. introduced him to the mostly Black audience as “the world’s greatest blues singer.”

And he was: the greatest singer of the blues idiom, or one of them.

I believe King’s key vocal influence was Roy Brown, a former boxer with a swooping tenor whose jubilant melodies sound like prototypical rock ’n’ roll. King’s own powerful, clenched tenor set him apart from all the other guitarists in pop music. Only when he took the stage with the likes of Bobby “Blue” Bland, one of the finest singers in any genre, did King meet his vocal match.

A 2008 Rolling Stone ranking tabulating the 100 greatest singers of all time placed Howlin’ Wolf, Bland, Muddy Waters, and John Lee Hooker above King, who, at No. 96, barely made the list at all. “The notes that King squeezes from his guitar, Lucille, are so sharp and pointed that it’s easy to overlook the sounds that emanate from his mouth,” the Rolling Stone editors wrote.

Not for the patrons who filed out of the Regal into the cold Chicago streets on that magical night.

Daniel de Visé’s King of the Blues: The Rise and Reign of B. B. King is out now from Grove Press