JACKSON (AP) — Corey Carter could hear snippets of music in his head — a calm and subtle melody that hadn’t found its shape. The 19-year-old college student simply needed a hero to visualize before he could finish his composition for wind ensemble.

He found inspiration in an unexpected place. And instead of a hero, he found a heroine.

Standing in line at a Walgreens’ one day a few months ago, he casually flipped through a book about African-American history in his hometown of Jackson, Miss. There, he ran across the 1961 mug shot of a jailed civil-rights worker.

The 19-year-old white woman had a calm but determined gaze. Her hair was neatly bobby-pinned, revealing a delicate earring in the shape of a cross. She wore her Sunday-best dress, a gingham check reminiscent of Dorothy’s in ‘‘The Wizard of Oz.’’

Around her neck hung a board with booking information for the Jackson city jail. She and other Freedom Riders had been arrested and charged with breach of peace after traveling in an integrated group, by train, from New Orleans.

‘‘It was just a very powerful image,’’ Carter recalled.

The woman in the mug shot was Joan Trumpauer, who grew up in northern Virginia and spent three years in the early 1960s working for racial equality in Mississippi, then one of the most defiantly segregated states in the nation.

Carter, a University of Southern Mississippi music major and aspiring film composer, saw a woman who did more than talk about racial equality — she lived it.

‘‘Once I was kind of thinking about that story, it took a turn where it all kind of morphed together and I could see where the piece was going,’’ he said. ‘‘I knew the piece then had something that there was a goal to.’’

In a matter of weeks, his ‘‘Power of Conviction’’ was dotted with the heroic refrains of trumpets, the clarion calls of trombones. Carter’s six-minute personal project was complete.

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Trumpauer — who would later marry and become Joan Trumpauer Mulholland — left Duke University in 1961. Defying the wishes of relatives who were steeped in a culture of segregation, she headed to Mississippi to work in the civil rights movement. She was inspired, she said, by the Bible’s call to love thy neighbor and the belief that all men are created equal.

‘‘What brought me to the movement was, basically, you could see the inequalities in life and the contradictions,’’ she told The Associated Press in a recent interview from her home in Arlington, Va.

She served her first three sweaty summer months for the breach-of-peace arrest in the Mississippi State Penitentiary at Parchman, now infamous for the beatings and other abuse Freedom Riders endured there.

After being released, she helped register voters and earned her degree as one of the few white students at traditionally black Tougaloo College in Jackson, a school that in the 1960s was a hub of activity for the expanding civil-rights movement.

One of her most frightening experiences came on May 28, 1963, when she helped challenge a whites-only policy at a lunch counter at Woolworth’s. She wasn’t even supposed to be there. Her assignment from Mississippi NAACP leader Medgar Evers — who would be assassinated about two weeks later — was to observe other civil-rights workers at a picket line elsewhere in downtown Jackson.

The picketers were quickly arrested, so Trumpauer Mulholland decided to see what was happening at Woolworth’s. The black college students trying to integrate the lunch counter were soon attacked by white teenagers and adults.

Anne Moody recalled in her memoir that she and fellow Tougaloo students Pearlena Lewis and Memphis Norman started praying at the lunch counter — and then ‘‘all hell broke loose.’’

‘‘A man rushed forward, threw Memphis from his seat, and slapped my face,’’ Moody wrote in the memoir, ‘‘Coming of Age in Mississippi.’’ ‘‘Then another man who worked in the store threw me against an adjoining counter.’’

Blood ran from the corners of Norman’s mouth as he lay on the floor, trying to protect his face as the man who threw him down repeatedly kicked him in the head. The workers, trained in a Gandhi-inspired discipline of nonviolence, never fought back.

‘‘If he had worn hard-soled shoes instead of sneakers, the first kick probably would have killed Memphis,’’ Moody wrote. ‘‘Finally a man dressed in plain clothes identified himself as a police officer and arrested Memphis and his attacker.’’

Trumpauer Mulholland said she and John Salter, a white Tougaloo professor who was active in the NAACP, went to the Woolworth’s counter to sit with the black civil-rights volunteers who were still there. The threat of violence was palpable.

‘‘The students that came down to observe us, the white high school students, started grabbing everything they could off the counter — mustard and ketchup and vinegar and salt and pepper and sugar. And some brass knuckles came into play, and cigarettes on the guys,’’ Trumpauer Mulholland said.

‘‘And once they ran out of condiments, they started grabbing things off the open counters, little junky things like they sell at dollar stores today, and throwing them at us and spray painting our backs and just generally tearing up the place and using it to attack us,’’ she said.

Several journalists recorded the scene, including photographer Fred Blackwell from the local Jackson Daily News. One of his images circulated worldwide on The Associated Press wire. It showed Salter, Trumpauer Mulholland and Moody sitting, apparently calmly, as they were doused with condiments and taunted by the mob for three hours. She said the media presence not only told the world what happened, but likely prevented the violence from escalating.

The civil-rights workers were able to leave in relative safety when the store closed that night, but only because Tougaloo president A.D. Biettel came to escort them out. Moody said in her memoir that outside the store, about 90 Jackson police officers formed a line between the small group and an angry white mob.

Trumpauer Mulholland, 67, says now that she felt as if she had a ‘‘disembodied spirit’’ during the sit-in.

‘‘The real me had left and was sort of keeping me safe,’’ she said. ‘‘And it was just the body there.’’

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This May, Trumpauer Mulholland flew to Mississippi for her Tougaloo class reunion, and she did something she never thought she’d do: She met a young, white Mississippian who admired and publicly honored her civil-rights work.

She heard an ensemble play the piece Carter wrote in her honor, ‘‘Power of Conviction,’’ at Jackson Academy, where about 98 percent of the 1,300 students are white. The academy is among hundreds of private schools that sprang up across the South after the U.S. Supreme Court ruled in 1954 that racially segregated public schools were unequal.

In Jackson, 97.6 percent of public school students are black; the more integrated schools are in nearby suburbs.

Carter is a graduate of Jackson Academy, and his father, Bruce Carter, has been band director there for 20 years. As the stage band learned ‘‘Power of Conviction,’’ Bruce Carter would show the young musicians the mug shot and Woolworth’s photo of Trumpauer Mulholland for inspiration.

Trumpauer Mulholland was astonished when the academy’s students gave her a standing ovation after she spoke at the band assembly — something she later said would’ve been unthinkable in a city where a previous generation of white high school students turned to mob violence to try to protect a segregated way of life.

The former Freedom Rider said her civil rights work prepared her well for her career as a teacher and made her a role model for her children and grandchildren. However, a rift grew between her and many of her relatives in the South. While younger relatives are cordial now, Trumpauer Mulholland said the connection with cousins her own age ‘‘pretty much fell apart.’’

‘‘My family, to the extent that I ever heard anything, really were upset with me and close to disowned me because I had just gone against everything they had grown up believing and feeling. And I was a traitor,’’ she said. ‘‘I think in many ways that made it easier as a white demonstrator, a white Southern demonstrator. Once you take a stand, there’s no turning back, so you may as well keep going forward.’’

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Tougaloo College: http://www.tougaloo.edu/

Jackson Academy: http://jastudents.org/jaweb/newhome/index2.php