“Love & Mercy,” a biopic about Brian Wilson, casts two actors as the musical genius behind The Beach Boys.

Off-putting as the unusual approach may be, it works. Beautiful and heartbreaking, “Love & Mercy” earns its place alongside the best biopics, including Oscar winners “Ray” and “Capote.”

Paul Dano (“12 Years a Slave,” “Little Miss Sunshine”) plays Wilson in his 20s in the 1960s. That’s when The Beach Boys — brothers Brian, Carl and Dennis Wilson, their cousin, Mike Love, and, at various times, guitarists Al Jardine and David Marks — released sun-kissed hits about girls, cars and surfing.

Fast forward about 20 years, and John Cusack tackles the challenging role of the older Wilson. In the 1980s, the long-reclusive music star is under the damaging influence of Los Angeles psychotherapist Dr. Eugene Landy.

The heroes and villains are obvious in “Love & Mercy.”

The obsessive, controlling Landy, viciously played by Paul Giamatti, takes the lead for 2015’s best movie villain. But as monstrous as Giamatti’s Landy can be, there are moments when he almost makes the case for the extreme treatment he gives Wilson.

Dano and Cusack are different in age and physical appearance, but each of them brings Wilson into vivid focus. Both performances bravely expose the composer-visionary’s struggles in affecting, authentic ways. Playing Wilson in his late 40s, Cusack is a wounded child in the body of a tortured middle-aged man. It’s his most memorable performance.

Although “Love & Mercy” moves back and forth between two eras throughout the film, there are no chronological jolts. Director Bill Pohlad (producer of “12 Years a Slave” and “The Tree of Life”) and screenwriters Oren Moverman (co-writer of the much less satisfying Bob Dylan biopic “I’m Not There”) and Michael Alan Lerner convey the parallel storytelling in clear and seamless style.

The Beach Boys’ early years are seen in quick, mostly breezy strokes, including a realistic re-creation of the group’s performance in the classic 1964 concert film “The T.A.M.I. Show.”

After a few years of stardom, the terrified Wilson suffers a meltdown on a plane. He withdraws from touring, telling his bandmates he’d rather work in the recording studio. And after Wilson hears The Beatles’ great 1965 album, “Rubber Soul,” he says: “We can’t let them get ahead of us. I’m going to make the greatest album ever made.”

Most of the film’s music appears in the ’60s part of the story. “Love & Mercy” follows Wilson into the studio as the feverishly inventive composer and arranger works with the best session musicians in Los Angeles, aka The Wrecking Crew.

It’s rare that a film gets music and musicians right. “Love & Mercy,” an indie production made outside of the major studios, is one of them. When Wilson joins The Wrecking Crew and classical musicians in recording studios to create his initially misunderstood and unappreciated masterpiece, “Pet Sounds,” the scenes look and sound genuine.

Wrecking Crew members Hal Blaine and Carol Kaye are actually supporting characters in “Love & Mercy.”

One revealing scene features Blaine reassuring the anxious Wilson on the night before the other Beach Boys are scheduled to record their “Pet Sounds” vocals.

“You gotta know you’re touched, kid,” the drummer says. “You’ve blown our minds.”

The Wilson brothers’ father, Murray, is another “Love & Mercy” villain. Played by Bill Camp (“12 Years a Slave,” “Birdman”), the merciless, abusive Murray is an obvious precedent for Landy. It’s easy to see how his oldest son, Brian, became so damaged. Beach Boy Mike Love (Jake Abel), who doesn’t recognize the artistic strides in “Pet Sounds,” comes off badly, too.

The film’s across-the-board exceptional performances continue with Elizabeth Banks’ portrayal of Wilson’s second wife, Melinda. It’s the most dramatic, nuanced role of her career.

In Banks’ first scene with Cusack, Wilson, still under Landy’s watch, writes a clandestine note on the back of Melinda’s business card. It says: “Lonely, scared, frightened.” Coming early in the film, it’s an unsettling moment, telegraphing the dark places this absorbing biopic dares to go before it finally finds the sun.