When Brian Wilson played the Non-Comm radio convention at the World Cafe Live in West Philadelphia this month, the 72-year-old songwriter sat center stage at the piano and introduced one of his most beloved compositions.

"Here's probably the best song I ever wrote, in 1966, off the Pet Sounds album," he said, before playing the song Paul McCartney has said is his favorite of all time. "It's called 'God Only Knows.' "

The rapturous reception the celebrated tune received, and with which it will undoubtedly be greeted when Wilson plays the Mann Center in Fairmount Park on June 29, contrasts mightily with the way it goes over on first hearing in Love & Mercy, the unconventional biopic directed by Bill Pohlad that stars both Paul Dano and John Cusack as the troubled songwriter. The movie opens Friday.

In the film, Dano, who plays the younger Wilson as he leads the Hawthorne, Calif., family band from the seaside escapism of "Fun, Fun, Fun" and "Surfin' U.S.A." into the deeper waters of Pet Sounds and its ill-fated follow-up, Smile, plays the song solo for an audience of one.

Upon hearing it, Wilson's domineering father, Murry Wilson, calls the song "wishy-washy." He suggests his son get back to writing more upbeat music or at least change the title. When Brian protests that "it's a love song," his dad corrects him: "It's a suicide note."

Later, after he's sold the publishing rights to the band's songs, Murry lets his son know how he really feels: "You've peaked, Brian. No one's going to remember you or the Beach Boys five years from now."

Love & Mercy is named after the tender title tune to a 1988 solo album. Wilson has called it "the most spiritual song I've ever written." The film is just one testament to the shortsighted wrongheadedness of his father's statement.

The esteem in which musicians hold Wilson, who said that in Smile he was writing a "teenage symphony to God," is best summed up in the movie by Hal Blaine, the L.A. drummer who captained the Wrecking Crew team of studio musicians who played on Pet Sounds. (Denny Tedesco's The Wrecking Crew documentary, which will be released on DVD on June 16, makes an excellent companion piece to Love & Mercy.)

Wilson worries over what his bandmates, who have been off touring Japan, might think of his Pets Sounds sounds. Blaine, played by Johnny Sneed, reassures him his talents are more copious than anyone the studio players have worked for, whether it be Frank Sinatra, Dean Martin, Elvis Presley, or Sam Cooke. "Phil Spector's got nothing on you," Blaine says, telling Wilson what he's most thrilled to hear. "You're touched, kid."

"It's really hard to overestimate his genius as an artist," said Cusack, who sat for an interview with Wilson and Pohlad during the South by Southwest Film festival in March in Austin, Texas, where Love & Mercy had its U.S. premiere.

But it was also really hard to tell the totality of Wilson's story - including his late-'60s drug-and-alcohol-hastened mental breakdown, and the 1970s and 1980s years spent under the suffocating care of controversial psychologist Eugene Landy - in one two-hour movie.

Or even, as Pohlad decided, with just one actor playing Wilson. The 58-year-old Love & Mercy director has been behind the camera only once before, on 1990's little-seen Old Explorers, but he has an impressive producer's resumé, including Brokeback Mountain and 12 Years a Slave. Pohlad is a lifelong Beach Boys fan, and Wilson's story originally came to his attention as a script titled Heroes & Villains, named after a hit song from the Smile sessions.

Along with heroes in Wilson and his second wife Melinda Ledbetter (Elizabeth Banks), Love & Mercy sports plenty of villains. Besides Murry Wilson, there's Mike Love, who upon hearing Pet Sounds, whines, "It's not Beach Boys fun. Even the happy songs are sad!" And a bewigged Paul Giamatti is frightening as Landy, a bad guy who can make a shouted-out beverage request - "Just make me a goddamn Arnold Palmer!" - the scariest thing you're likely to hear all summer.

Pohlad, though, didn't like the approach of Michael Alan Lerner's original script for the movie, which Pohlad wanted to be about not good guys and bad guys, but the depth of Wilson's brilliance.

Working with screenwriter Oren Moverman, he took a dual approach to the story, which cuts back and forth between the band's '60s rise and the romance between Wilson and Ledbetter, whom he meets when shopping for a Fleetwood in the Cadillac showroom where she works.

Before being whisked away by the always-watchful Landy and his henchmen, Wilson leaves the woman who turns out to be the angel of his redemption a business card with three words scrawled on it: "Lonely, Scared, Frightened."

"The biopic is a trap," said Pohlad, seated between the hulking, mostly stone-faced Wilson and Cusack in a South by Southwest conference room, explaining his two-sided approach that deftly cuts back and forth in time. "We knew we needed to have Pet Sounds in there," he said of the classic album, which Wilson calls "the high point for me artistically."

"Starting with the early days, it was really fun-filled," Pohlad said. "Then Melinda telling the story of how they met, that seemed like a good way of getting the audience into it. And when John came on, we were into this really heavy stuff."

The film's subject was on set for much of the shoot, and along with his wife, with whom he has five children, he met extensively with Cusack, who also researched the role by listening extensively to the enthralling Pet Sounds and Smile session tapes ("That's where I lived," Cusack said).

Watching his life reenacted before his eyes was an uncomfortable but rewarding experience, Wilson said.

"The actors were cast so well, especially Dr. Landy," said Wilson, whose show at the Mann is in support of his better-than-you-might-expect goofily titled new album, No Pier Pressure. "Every bit of yelling, everything that he did, I went through the whole process again. And I was so relieved when it was over. It was hard for me to face up to it. I thought it was actually Dr. Landy himself in the movie. So you can imagine how I felt."

Cusack - who is compelling as a childlike, guileless man in need of a great deal of help as he tries to put his life back together - purposefully did not consult with Dano to share strategies.

"We wanted it to be two different impressions," said the actor, 48, who called Wilson "a real survivor in a way that people don't fully understand, with everything he's gone through."

"It was really done by feel," Cusack said of Love & Mercy. "It was admitting there are different aspects to Brian's life and personality. I think that speaks to the concept that no one film can tell the entire story of a person's life."

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