The lead singer of the country-rock band Lukas Nelson & Promise of the Real is inhaling a bit more of that vapor as he prepares for the opening of “A Star Is Born,” a movie remake about a rising musician featuring songs Mr. Nelson helped write and perform.

The 29-year-old son of country-music legend Willie Nelson, Lukas Nelson joined the movie as an adviser to its director and star, Bradley Cooper. He was hired to keep the concert scenes feeling authentic while Mr. Cooper performed as the seasoned musician Jackson Maine.

That job morphed into a larger role as Mr. Nelson began writing songs with Mr. Cooper at his Los Angeles home and brainstorming tracks with Lady Gaga, who plays the breakthrough singer in the film. Mr. Nelson co-wrote eight songs and appears on-screen with his band, backing Jackson Maine.

Mr. Nelson spoke with the Journal about inspirational seagulls, what he learned from his father’s work with Snoop Dogg and the childhood anxiety dream that predicted his future. Here are edited excerpts from the conversation:

Do you feel swept up in the premiere of “A Star Is Born”?

I’m exercising a lot, meditating, stretching and doing yoga. Trying to stay grounded as things come in and recognize that success is a product of inspiration.

How did you go from an adviser on the film to songwriting and performing?

We were trying to find the character of who Jackson Maine was. The songwriting sort of helped shape that. It was a natural process of evolution, just the fact that I was there and I do write. I’m spending all this time creating this character, I might as well write for this character and see what he thinks.

How is Bradley Cooper as a songwriter?

He had a lot of great ideas. He would sing me the notes of solos he wanted me to play. He’s a very musical guy. He was inspired when I’d say, “You know, that’s actually good.” That’s really all you need, is support from people around you and honesty when it could be better.

What music clichés did you try to avoid?

We wanted somebody with his own style, someone with his own voice and something to say. Stereotypes are no fun and you don’t want to do something that’s been done before. That’s an artist’s worst nightmare, to be stuck in something, that’s like being in prison. Look at Dad—he’s done a reggae album, he’s done a song with Snoop Dogg, he’s done a bunch of stuff all over.

Did you feel you were destined to become a musician?

Yeah. I had a dream when I was, like, 6 years old, that I was on stage in front of hundreds of thousands of people. I was singing and I was terrified. And then a voice told me to shrink down into my chest and look out at the audience through my chest, which I woke up and years later realized it was just a metaphor, like coming from the heart. Because I felt safe in that place, and when I started to sing from that place, the crowd went wild.

Do you think about the downsides of fame?

I think about that, but then I also say, “OK, stop thinking.” You know, I’m studying math now. I’m going back into calculus and reviewing algebra. Really, I think the only purpose of being alive is learning and growing and creating. I didn’t pay attention in school because I was paying attention to learning guitar. It doesn’t mean I don’t want to know these things and be able to understand the universe and the world around me.

Did anything happen on set that you never would have predicted?

The only time I’m good at predicting something is if I can see a pattern I can recognize. In chess, I can predict a few moves ahead of time. As a child I tried to build my foundation musically. I practice every day, that’s all I focus on, is just getting as good as I can at what I do.

A book I read as a kid, “Jonathan Livingston Seagull,” is about all these seagulls, all they can think about is just fighting over food and eating. And this seagull is like, “No. I want to learn how to fly as fast as I possibly can.”

He spends all day away from the crowd just practicing his aerodynamics, getting as fast as he can, flying as fast as he can just for the ultimate joy of flying.

The rest of the guys hate him. They think, “He’s weird. Why aren’t you trying to eat?” And he’s like, “I just want to fly.”

I won’t give away the whole rest of the book. It’s a very beautiful book.

Has your dad seen the movie?

Not yet. We just have to coordinate between all of us. Just seeing each other is a big deal.

Are you texting with Bradley Cooper—are you guys friends now?

We’re very close. He’s a fantastic dude. We connected very deeply. As a human being, he’s such a hard worker and he meditates every day. He seems very grounded to me.

I read that your mom wouldn’t let you play guitar in Bob Dylan’s band when you were in high school. Were you mad at her?

No, I didn’t even know it had happened until a little later. I love Bob Dylan to death. I think he’s a fantastic human being. I would’ve gone for sure had I had the choice.

Do you like watching yourself on-screen?

Well, you know, I don’t cringe. That’s a good sign.

Write to Ellen Gamerman at ellen.gamerman@wsj.com