Half a century ago, on March 7, 1965, state troopers knocked down, gassed, and beat a number of men and women who were participating in a peaceful march for voting rights in Selma, Alabama. That same day, radio listeners around the country might have heard Sam Cooke singing a lyric he’d written and recorded several months earlier, but which could have been describing the “Bloody Sunday” confrontation on the Edmund Pettus Bridge.

_Then I go to my brother

_ _And I say, “Brother, help me please.”

_ _But he winds up knockin’ me

_ Back down on my knees.

Like the Selma-to-Montgomery march, Cooke’s brooding but bright civil-rights anthem “A Change Is Gonna Come” recently marked its fiftieth anniversary. The song, which was released as the B-side of Cooke’s posthumous hit single “Shake” just days after his funeral, in December 1964, entered the national pop and R&B charts during the first week of 1965. It fell off the pop countdown, after peaking at No. 31, on March 13th, and would slip from the R&B charts, where it climbed to No. 9, on April 10.

These anniversaries have passed without much commemoration—somewhat surprisingly, given that Cooke’s recording remains as beloved and as timely as ever. Then again, it may be that the song’s persistent relevance explains the neglect. The serial shootings of unarmed black men by law enforcement; the Justice Department report on police abuse and corruption in Ferguson, Missouri; the gutting of a Voting Rights Act provision that was one key consequence of the Selma marches—these and other dispiriting headlines have perhaps rendered the confident optimism of Cooke’s masterpiece difficult to sing along to without seeming naïve. If Cooke were alive to update “A Change Is Gonna Come” for the current political scene, he might be tempted to rename it “The More Things Change.”

In a story that has come to symbolize the ways in which American popular music intersected with and helped sustain the civil-rights movement, Cooke was motivated to write “A Change Is Gonna Come” by another sixties anthem, Bob Dylan’s “Blowin’ in the Wind.” When he first heard that song, Peter Guralnick writes in 2005’s “Dream Boogie: The Triumph of Sam Cooke,” he “was so carried away with the message, and the fact that a white boy had written it, that . . . he was almost ashamed not to have written something like that himself.”

The soul singer and former gospel star was further inspired when he heard Peter, Paul and Mary singing Dylan’s song on the radio. As Daniel Wolff explains in his 1995 biography of Cooke, “You Send Me: The Life and Times of Sam Cooke,”_ _the folk trio piqued Cooke’s commercial ambitions. Their recording proved that “a tune could address civil rights and go to No. 2 on the pop charts.” For Cooke, the result of these racial and artistic challenges was “A Change Is Gonna Come.”

As origin stories go, this one is satisfyingly precise and frustratingly incomplete. It pinpoints exactly what prodded Cooke to write a civil-rights-themed protest song, but says nothing about the specific protest song Cooke wound up writing, let alone the record he created (a key distinction, which is too often elided).

For one thing, “Change” delivers a message notably distinct from Dylan’s in “Blowin’ in the Wind.” On the recording, Dylan is obviously concerned about the troubles he’s addressing, but his flat delivery conveys none of the urgency, hope, or confidence that are so paramount in Cooke’s performance. Soon afterward, Dylan would write “Only a Pawn in Their Game,” in response to the murder of Medgar Evers, and he would travel to Greenwood, Mississippi, in support of voter registration, and perform at the March on Washington for Jobs and Freedom. But the Dylan of “Blowin’ in the Wind” muses over important issues from a third-person distance that Cooke’s song (“I was born by the river…”) eschews from the jump. Dylan poses philosophical musings and rhetorical questions amid antiquated word choices (in the days of “Ban the Bomb,” he’s going on about “cannonballs”), geological time frames (those washed-to-the-sea mountains), and Old Testament allusions. “Blowin’ in the Wind” intimates that the answers we crave are where they have always been and where, tragically, they may well remain. “A Change Is Gonna Come” is unequivocal.

The two recordings also sound as unlike one another as two early-sixties records could: Cooke and Dylan were wading up different streams of the American song for inspiration. Dylan found much of his melody in the nineteenth-century black spiritual “No More Auction Block for Me” (also known as “Many Thousands Gone,” which was a source for another anthem of the era, “We Shall Overcome”), while his voice and phrasing, and his austere and static strum, are indebted to the Depression-era folk style of Woody Guthrie. By contrast, the melody to “A Change Is Gonna Come,” with its long dynamic lines that trek the peaks and valleys of arranger René Hall’s lush orchestral landscape, shows Cooke working off of Tin Pan Alley standards, film music, and show tunes.

“Change” opens with a regal assemblage of strings, buffeted and borne heavenward by kettledrum and French horn, all of which build theatrically and then clear out quickly for Cooke’s entrance—you can imagine the singer moving downstage into a spotlight, or a camera zooming to close-up. But while the musical setting is grandiloquent, Cooke’s tale is down-to-earth. He was born alongside a river that, like him, has never stopped rolling. He’s been run off when trying to see a movie downtown and beaten to his knees when asking for help. He’s had his moments of fear and doubt, but through it all—big finish—he’s nurtured a faith, now a conviction, that change is on the way. Cue tympani.

None of this sounds or feels like “Blowin’ in the Wind.” It sounds like “Ol’ Man River.”

The comparison isn’t arbitrary; we know that Cooke was familiar with the song, which was written by Jerome Kern and Oscar Hammerstein’s 1927 musical “Show Boat.” He included a version of it, alongside “Summertime” and other Great American Songbook classics on his 1958 début album. “I gets weary and sick of tryin’ / I’m tired of livin’ and scared of dyin’,” he sings in his oddly smooth and swinging performance of the Kern-Hammerstein tune. Six years later, he would transform those lines in the second verse of “A Change Is Gonna Come”: “It’s been too hard livin’, but I’m afraid to die.”

That fairly direct allusion has been remarkably little noted, at least in print. In his new book,“Who Should Sing ‘Ol’ Man River’?: The Lives of an American Song,” Todd Decker notes only that Cooke’s song, like the Kern-Hammerstein composition, mentions a river. More helpfully, he observes that “the most prolific and engaged era for ‘Ol’ Man River’,” the years in which it was most often included on albums and performed on TV, stretched from the late nineteen-fifties well into the nineteen-sixties. To cite only one example out of dozens, Ray Charles released a version “Ol’ Man River” in 1963 that nicely anticipates the slow pacing, heartfelt delivery, and big, old-school pop arrangement of “A Change Is Gonna Come.” In 1964, Dylan’s wasn’t the only racially themed protest song that was blowing in the wind.