Nina Simone was born Eunice Kathleen Waymon in 1933, in the small town of Tryon, N.C., but she changed her name in the mid-1950s so that her family and the townspeople who had funded her study at Juilliard School of Music wouldn’t know she was playing lounges in New York City. Rather than be torn between her formal training and the education offered by smoky nightclubs, she blended the two into a unique soundclassically focused, yet shot through with jazz rhythms and wild vocal improvisations.

Simone remained a student of music all her life, and the new four-disc set To Be Free: The Nina Simone Story chronicles her experiments with be-bop, funk, rock, folk, blues, r&b, show tunes, world music and what even sounds like rap. These 51 adventurous tracks portray her as one of the 20th century’s great synthesizers, absorbing every style and sound she heard into her one sterling repertory.

In the long run, Simone ought not to have worried about her family’s disappointment: Her reputation as an intense performer led to her signing with the Bethlehem imprint of King Records, for whom she made her first recordings. Her versions of Duke Ellington’s “Mood Indigo,” the Gershwins’ “I Loves You, Porgy,” and the pop standard “My Baby Just Cares for Me” are full of unexpected turns of vocal phrase and intuitive piano performances, pointing the way toward more idiosyncratic material like her interpretations of Kurt Weill’s “Pirate Jenny” and Jacques Brel’s chanson “Ne Me Quitte Pas.”

The development and expansion of her sound seems in retrospect not simply a circumstance of her musical restlessness, but also a response to the events happening around her: the bloody Civil Rights movement, Vietnam, the assassinations of Robert Kennedy and Martin Luther King Jr. In 1964, a year after the murder of civil rights worker Medgar Evers in Mississippi and the Baptist church bombing in Alabama that killed four young girls, Simone wrote what may be her most famous composition (and one of very few, as she was not an especially prolific composer), titled “Mississippi Goddam,” which describes the craziness of the South in no uncertain terms: “Alabama’s got me so upset, Tennessee made me lose my rest,” she sings as she plays an almost jaunty piano theme, her anger rising throughout the final line of the chorus: “And everybody knows about Mississippi goddam!”

That the song only exists in live recordingsincluding the one on To Be Free, captured just days after the assassination of Kingmakes it all the more potent. She challenges and chides her audience. She’s up there, singing about the mess. What were they doing besides sitting, listening?

Simone sounds powerful and authoritative in her dissent, which was all the more potent for being packaged in a style more popularly associated with sentimental displays of emotion. “I want to shake people up so bad that when they leave a nightclub where I’ve performed, I just want them to be to pieces,” she states in the 1970 television special NINA: A Historical Perspective, included on the set’s accompanying DVD.

That dissent, however, is not all there is to Simone, who remained at all times an incredibly physical singer. Her music was a sculpting medium. She digs at her notes, molds them into curious shapes. During the 18 swinging minutes of her “My Sweet Lord/ Today Is a Killer” (performed live for predominantly black servicemen at Fort Dix, N.J., in 1971), she reshapes a George Harrison melody into a gospel disquisition. It’s not a song, it’s a sermon. Her frenetic cover of Richie Havens’ “No Opportunity Necessary, No Experience Needed” (on CD for the first time here) is something more sinister. She scats, racing the driving percussion, then raising her voice into an accusatory shout. “Feeling Good,” from 1965, sounds more hopeful and gentler as Simone gives the lovestruck lyrics a deeper, graver reading. But she ends the song with an ecstatic burst of scatted syllables.

Of her generation, only Betty Carter could scat harder or more instrumentally, but no one could match her defiant assertiveness. Simone never let her audiences take her race or her gender at face value, so she constantly had to define and redefine herself through music. There’s “Mississippi Goddam” of course, and the heartbreaking “I Wish I Knew How It Would Feel to Be Free.”

There’s her witchy, straight-faced take on Screamin’ Jay Hawkins’ “I Put a Spell on You,” as well as a handful of Dylan covers. The one that stands out most dramatically isn’t her churchly “The Times They Are A’Changin’”who didn’t cover that song in the ’60s?but her version of “Just Like a Woman,” one of Dylan’s least generous songs. Simone’s voice sounds tender and knowing, signaling that she identifies with these romantic and social bruises, and on the final chorus, she switches from third-person to first: “I take just like a woman, and I make love just like a woman/ but I break just like a little girl.” It’s a powerful moment not simply because she has the temerity to rewrite Dylan, but because she accepts rather than rejects all those freighted gender assumptions. She explodes the song’s possibilities in ways Dylan didn’t.

Five years after her death, Simone would seem to have more relevance than ever, especially considering the election of the first African-American president and the roles race and gender played in a long and divisive campaign. True, Simone might have been heartened at the outcome, but such a statement seems little more than superficial: Her music would be just as relevant, albeit in a very different sense, if Barack Obama had lost.

Besides, in the late ’60s and early ’70s, Simone had no reason to be hopeful about race relationsshe laces “Mississippi Goddam” with the provocative declaration “I ain’t ’bout to be nonviolent, honey!”

To Be Free cannot re-create the risk involved in taking that stance at that time and in that style of music; all it can show is how her politics motivated and broadened her music, instilling in it an urgency that remains palpable years later. Her beliefs made her brave, her music made her singular, and both leave us listeners to pieces.

Stephen M. Deusner has been a staff writer at Pitchfork Media since 2004. His writing has also appeared in The Memphis Flyer and Harp. He lives in Washington, D.C.

Correction (Nov. 20, 2008): It has been five years since Simone’s death.