For someone who just watched John Cusack portray the Beach Boys’ legendary Brian Wilson in “Love & Mercy,” it was a bit surreal to sit down with both Cusack and Wilson recently to chat about the making of the film.

Yet from the get-go, it was clear both men not only have enormous respect for each other’s gifts, but also a strong bond and deep affection has developed between the two of them. In particular, Cusack’s body language exhibited an almost reverse paternal caring for Wilson, as the actor constantly was attentive to the musical icon’s comfort as he sat next to him during our chat at the Metro Chicago club on the city’s North Side.

Asked for his reaction to the work of Cusack and Paul Dano as Wilson’s younger self in “Love & Mercy” (opening Friday), Wilson didn’t hesitate to say, “John is a genius at what he does, and Paul Dano is a genius at what he did [in the film].” That rave remark led Cusack to quip, “There’s tape in that [recorder] right?”

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Yet turning serious, the Chicago native explained that making the film was truly a labor of love for all concerned. “Everybody involved, including the actors like me, Paul Giamatti [who portrays Dr. Eugene Landy, the disturbed psychologist who treated Wilson for a time], Paul Dano and Elizabeth Banks [who plays Wilson’s eventual wife Melinda] to the people on the crew — everybody was so aware of the legacy of Brian’s music,” said Cusack. “It really wasn’t about doing it for the money or looking at it as simply doing a job. Everybody wanted to be there and understood this was a once-in-a-lifetime opportunity.”

For Wilson, watching the completed film was a revelation as well. “I was amazed at how accurate it was. Not only were John and Paul right in how they played me, but Paul Giamatti was letter-perfect in playing Dr. Landy,” said the Beach Boys co-founder. “So letter-perfect, it was scary and disturbing for me to watch that part of my life again. It brought back a lot of emotion from that period of my life.”

The uneasiness was understandable, as Landy took total control of the musician’s life for several years — forcing him to cut off contact with his family and controlling him with brain-numbing drugs and various psychological tactics that made him a virtual prisoner in his own house. Before Wilson’s family was able to get court-ordered motions, Landy had even gone so far as to control Wilson’s financial affairs and estate planning.

Asked how he prepared to play the older Brian in “Love & Mercy,” Cusack said he was able to watch a lot of footage from the early years of the Beach Boys.

“But then he removed himself from public life for a bit, for the reasons the movie goes into — all the stuff with Dr. Landy and so forth,” said Cusack. “Then he emerged in the ’80s after falling in love with his wife Melinda.”

The actor was “lucky enough to talk to Brian and talk to Melinda and to talk to people who were in his life at that time, to try and understand what he was going through.

“But most important, Brian was so gracious to talk to me and I could always listen to his music. I could find Brian’s essence in his music. … I just immersed myself in his music because I think everything in Brian is related to his music — the way he sings and plays.”

For Cusack, Wilson’s long struggle to keep moving forward musically — and not repeat himself as an artist — was something familiar. “It’s about the whole concept of creativity. Whether you’re an actor or an artist or a painter or a musician — whatever you are going to do in the arts — sometimes there are people around you who want you to do something you’ve already done.

“That’s happened to me, it’s happened to every artist I know, and  it happened to Brian on such a massive scale, even as he was changing the musical world so much.”

For the actor, that struggle is something that even those of us without musical talent will understand. “I think everyone watching this film will relate to Brian’s struggle to break new ground with his creativity and his attempt to avoid being stuck in the same place forever.”

Cusack’s own love of music is well-known. The actor said, “Soundtracks have always been an important part of filmmaking for me. Even as an actor I also come up with a soundtrack that I think will be right in my head for the character I would be playing. While doing the role I listen to that music over and over and over again. It really helps me focus in on the role.

“In the past, I’ve used Brian’s music for other characters I’ve played. But the nice thing this time — I didn’t have to listen to anybody else. It was all Brian Wilson’s music all the time. I was the luckiest guy in the world.”