In a defining moment at the beginning of Cameron Crowe’s paean to pop music and his roots as a teenage rock journalist, the sister of Crowe alter-ego William, sneaks home an album by Simon & Garfunkle — not exactly the bad boys of late ’60s rock ‘n’ roll. Nevertheless, Anita’s mother Elaine (Frances McDormand) dismisses the record as “the poetry of drugs and promiscuous sex.”

“Honey,” she says pointing to the duo’s rather innocuous portrait on the album cover, “they’re on pot.”

The encounter could have painted Elaine as shrill, puritanical and narrow-minded. But in that very same scene we see that while Elaine might be strident, she also reveals a calmness and malleability in the face of her daughter’s rage. Elaine might rail against the mindless trappings of adolescent rebellion, but she also encourages her kids to be non-conformists. “Follow your dream,” she tells William.

McDormand, who won an Oscar as quirky detective Marge Gunderson in “Fargo,” was able to navigate the character’s seemingly dichotomous dimensions with a screen veteran’s savvy.

“One of the beauties of Frances is that she gives you deep humor and deep pain at the same time,” Crowe says.The director wrote Elaine as a college professor who, he says, “is understood by her students but not her children.” He adds that McDormand’s idiosyncratic spin was to make it very personal. “Her own relationship with her son is very powerful, and I think she’s a parent first in many ways, so this wasn’t a frivolous task for her,” says the writer-director. “It just felt like you were spying on life because she makes everything so real.”

The role earned McDormand a Golden Globe nomination and best supporting actress honors from the Los Angeles Film Critics Assn. and the Broadcast Film Critics Assn., both of which also cited her work in “The Wonder Boys.”

Adds “Wonder Boys” director Curtis Hanson: “She’s so watchable because she’s such a talent and has an energy that comes from an intelligence and depth that keeps you guessing.”