“I want to shake people up. I want to shake people up more.” These words were once spoken by international super-artist Nina Simone. It’s safe to say she succeeded with her mission: More than 50 years after her debut, few can match Simone’s supreme gifts as a vocalist, pianist, and arranger, the diversity of her repertoire, and the way those songs rattled consciences. Her music’s agelessness, as well as her delivery, has kept the melodies, as well as her message, fresh. And though her contribution to rock ‘n’ roll isn’t the first thing you may think of when it comes to her virtues, Simone was what we call a rocker: Her fierce attitude and the way she adapted some of rock’s best-known songs contributed toward getting across her message of true liberation.

“What we were looking for then was to shake people out of their complacency,” says Al Schackman, Simone’s musical soulmate and foremost collaborator. Schackman served as the genre-defying artist’s musical director, as well as a multi-instrumentalist, guitarist, and musical companion for just about the entirety of her career; the pair shared what both have described as a rare, telepathic communication that served them onstage as well as off. Much of their work together was compiled in 2008 on the four-disc set To Be Free: The Nina Simone Story, which includes a hefty slice of Simone’s “rock” repertoire alongside the jazz, folk, standards, and originals for which she is otherwise famous.

“If you wanted to classify her, she said she was a folk artist,” says Schackman, a Greenwich Village folk scene regular himself, though that isn’t necessarily the kind of folk Simone was talking about. She sang the songs indigenous to a country’s and people’s origins, from New Orleans and the “House of the Rising Sun” to Nigeria and Olatunji’s “Zungo”; she also interpreted Jacques Brel’s “Ne Me Quitte Pas” and the European ballad “Black Is the Color of My True Love’s Hair”, among other folk tunes.

For the album To Love Somebody, she took on “Turn! Turn! Turn!” from the folk-rock canon and turned it into a laidback jam. What Pete Seeger had borrowed from the Bible and what the Byrds turned into a reverent folk-rock cover, Simone deconstructed, finding the song’s soul. Another one of her great performances is the self-celebratory “Ain’t Got No/I Got Life” from Hair: The American Tribal Love-Rock Musical. She turned in versions of singer-songwriter classics like Sandy Denny’s “Who Knows Where the Time Goes”, Leonard Cohen’s “Suzanne”, and Randy Newman’s “Baltimore.” And while George Harrison and Richie Havens were songwriters she relied on more than once, their guitar strums and worldviews apparently music to her ears, she could also sing the blues. Simone was a full-service song interpreter.

“Oh yeah, Screamin’ Jay Hawkins,” says Schackman. “‘I Put a Spell on You.’ He wrote that song like a comedy, like he was the big magician, having fun with it. When she did it, it was dead serious… ‘I put a spell on you, the things you do, don’t you lie’… it was a warning. She’s tellin’ her man, ‘You’d better be cool.’ We did the Guinness Blues Festival in Dublin and Screamin’ Jay was there too, and he came back into the dressing room and he kneeled down in front of her and said, ‘The song was never done ’til you did it.’

“When she did a piece of music, she would claim it as her own. Because it would change totally,” he says, pointing to a version of “Revolution” by the Beatles, as customized by Simone for her own purposes in 1969, one of the most famously intense years in 20th century history.

“The people were directly involved and affected by what was going on… she wanted to make sure that they were really shaken out of what she felt was their sleep. One of the ways that we did that was like really blasting off on the tune, ‘Revolution’, where at the end we try to set off an atomic bomb, that kind of thing. People weren’t expecting that out of her at that time. To all intents and purposes, that one particular piece was a real departure from what her music was known for. It bordered on—I can’t say rock—but it kind of had that feeling.

“In the interludes, in the little breaks, she wanted me to get as far out as possible on the guitar. I used a slide to just really be able to make like explosive sounds… I would be playing notes using the slide,” as when Schackman plays the familiar Elmore James lick the Beatles borrowed for “For You Blue.” “But in the end, I took that slide and just went nuts on it, totally explosive.”

Simone had a rare musical gift, and her commitment as a fierce freedom fighter elevated her stature as an internationally understood and sometimes misunderstood vocalist. Her uncompromising attitude at crossing music with politics put her in a class with musical rebels, from Marvin Gaye and Chuck D to Bob Dylan and John Lennon. Not only did she use her originals like “Mississippi Goddam” and “Four Women” to convey her feelings on race matters, she worked in established pieces like Brecht-Weill’s “Pirate Jenny” to rouse audiences. “‘Pirate Jenny’ will scare the hell out of you the way she did it,” says Schackman. “There were people that came to concerts, like a family with a young kid… and during that song they’d leave. They’d get up and leave the concert ’cause of her language. She was ‘Pirate Jenny.’”

I asked Schackman how he tackled Simone’s notoriously fiery nature. “At times it was very difficult. A couple of times it was dangerous,” he says, though he maintains that Simone’s unpredictable disposition contributed positively to her creative process, especially to her unparalleled intensity onstage. “It helped her to be able to take on different characters. On one night, a song might have one type of character, and on another night, it would have a totally different character. It was wonderful—amazing.” He seeks to clarify that drugs never fueled her: “I can tell you she wasn’t a junkie. She didn’t do dope.”

As Simone famously shifted gears from Duke Ellington to Jimmy Webb, there were certain songwriters she favored: She wrapped her voice around Bob Dylan’s “Just Like Tom Thumb’s Blues”, “Just Like a Woman”, and “The Times They Are A-Changin’” as well as the perhaps unlikely Bee Gees, who she ended up covering four times. She gave a psychedelic soul shot to “To Love Somebody”, turned in a breezy “In the Morning”, and also laid down two lesser-known numbers, “Please Read Me” and “I Can’t See Nobody.” According to the liner notes of To Be Free, Simone was turned on to the British-Australian trio by Animals singer, Eric Burdon.

Schackman tells a story of the night in 1964, backstage at the Village Gate, when Simone and Burdon first met. “One time, Art D’Lugoff, the owner of the Village Gate, brought an artist back to see Nina, and he said he was like, her biggest fan. He told her what a fan he was and that she had inspired him… and she attacked him for stealing her song… this white guy had stolen ‘her song.’  I’ll never forget that. He was scared half out of his mind.”