In the movie musical, Garfield plays the creator of “Rent,” who died unexpectedly at 35. Making the film helped Garfield process a death in his own life.Jon (Andrew Garfield) is throwing a party, though there’s hardly a reason to celebrate. He’s riven with anxiety, his cramped apartment is overpacked with people, and he’s just spent money he doesn’t have, a down payment on success that will not come within his lifetime. But still, with a wide grin, Jon toasts his friends, leaps on his couch and sings, “This is the life!”Jon is Jonathan Larson, the composer and playwright who died suddenly of an aortic aneurysm at age 35 in 1996 just before his new musical, “Rent,” would become a global smash. The new film “Tick, Tick … Boom!” portrays Larson struggling to find success in his late 20s, as he frets about whether he should pack it in and choose a more conventional path than scripting musical theater.Larson originally created “Tick, Tick … Boom!” as a solo show, “Boho Days,” starring himself in 1990; after his death, it was reworked by the playwright David Auburn into a three-person production that the “Hamilton” creator, Lin-Manuel Miranda, saw in 2001, when he was still a senior in college.“Here’s this posthumous musical from the guy who made me want to write musicals in the first place,” said Miranda, who’s now made his feature directorial debut with the film.Miranda saw Garfield in the 2018 Broadway production of “Angels in America” and thought he was “transcendent” in that show. “I just left thinking, ‘Oh, that guy can do anything,’” the director recalled. “I didn’t know if he could sing, but I just felt like he could do anything. So I cast him in my head probably a year before I talked to him about it.”Miranda put Garfield through his paces, sending him to a vocal coach and ensuring that the actor would be able to play enough piano so the camera could pan from his fingers to his face throughout the film. But those are just the technical aspects of a performance that is impressively possessed: Garfield plays the passionate, frustrated Larson with enough zealous verve to power all the lights on Broadway.Garfield as Jonathan Larson in a scene from “Tick, Tick … Boom.”Macall Polay/NetflixIt’s all part of a very busy fall for the 38-year-old actor, who recently appeared in “The Eyes of Tammy Faye” as the disgraced televangelist Jim Bakker and, it’s rumored, will suit up alongside Tom Holland and Tobey Maguire in “Spider-Man: No Way Home,” out in December. (Of that supersecret superhero team-up, Garfield can divulge nothing.) Still, it’s clear that “Tick, Tick … Boom!” meant much more to him than he initially expected.“It’s a strange thing when there’s someone like Jon that you didn’t have any relationship to before, and then suddenly now there’s this mysterious forever connection that I am never, ever going to let go,” Garfield told me on a recent video call from Calgary, Canada, where he’s shooting “Under the Banner of Heaven,” a limited series. “I just feel so lucky that Jon was revealed to me, because now I don’t remember who I was before I knew who Jon was.”Here are edited excerpts from our conversation.How did “Tick, Tick … Boom!” originally come to you?One of my best friends in New York is Gregg Miele, and he’s the great body worker and massage person of New York City — he works on all the dancers and actors and singers on Broadway and beyond. Lin was on his table one morning and asked, “Can Andrew Garfield sing?” And Gregg, being the friend that he is, just started lying, basically, and said, “Yes, he is the greatest singer I’ve ever heard.” Then he called me and said, “Hey, go and get some singing lessons because Lin’s going to ask you to do something.”Lin and I had lunch, and he told me briefly about “Tick, Tick” and Jon. I’m not a musical theater guy in my history — it’s not something that I’ve been introduced to until the last few years, really. So Lin left me with a copy of the music and lyrics, and he wrote at the front of it, “This won’t make sense now, but it will. Siempre, Lin.”Garfield hadn’t done much singing when he was cast in “Tick, Tick … Boom” opposite musical theater veterans. “I’m like, ‘Oh my God, I’m going to die.’”Alana Paterson for The New York TimesYou’ve performed in plays like “Angels in America” and “Death of a Salesman” on Broadway, but in this film, Lin surrounded you with a lot of musical-theater ringers, and even some of the smallest roles and cameos are filled by major players from that world. That had to have been a daunting space to step into.I remember a very specific moment where we were in music rehearsal. Alex Lacamoire was at the piano walking us through the songs — he’s Lin’s musical arranger and producer — and I was with [“Tick, Tick” co-stars] Robin de Jesus and Vanessa Hudgens and Josh Henry and Alex Shipp. You can imagine how I’m feeling! They’re all just pros, they know exactly what they’re doing, they’re making notes. I’m like, “Oh my God, I’m going to die.”Then it comes time for me to get into the song and I’m just trying to get through it. I remember Alex Lacamoire going, “Woo, Andrew!” And then everyone behind him, like Josh and Vanessa and Alex and Robin, were like, “Yeah baby, that’s it baby! You got it, baby!” I go beet red and five minutes pass, and I’m just like, “Hey guys, sorry.” I start crying, and I say, “I don’t know if I’ve ever been this happy in my entire life, to be surrounded by the most supportive liars I have ever known.”Garfield working with his director, Lin-Manuel Miranda, who cast him after seeing the actor in “Angeles in America.” Miranda recalled, “I didn’t know if he could sing, but I just felt like he could do anything.”Macall Polay/NetflixJonathan spends the movie anxious about this ticking that only he can hear. How did you interpret that?There was a line in the original one-man show “Boho Days”: “Sometimes, I feel like my heart is going to explode.” It was too on-the-nose for people after he passed away, and they had to cut it, but he spends the story trying to figure out what this ticking is: “Is it turning 30? Is it that I haven’t succeeded? Is it some unconscious idea of my girlfriend’s biological clock combined with the pressure of my career? Or is it all of my friends who are losing their lives at a very young age because of the AIDS epidemic?”It could even be a musical metronome. The way you play Jonathan, as this theatrical person who feels so deeply and urgently, it’s almost like he needs to break into song because normal life just doesn’t cut it.Everything is up at an 11. Even when he’s making love, it’s at 11! Somehow he knows that this is all going to end, that this is all so ephemeral, and I think he was acutely, painfully aware that he wasn’t going to get all of his song sung. And I think he was also agonizingly aware that he wasn’t going to get the reflection and recognition that he knew he was supposed to have while he was still breathing.On the last day of shooting, what I understood is that Jon had it figured out. He knew that this is a short ride and a sacred one, and he had a lot of keys and secrets to how to live with ourselves and with each other and how to make meaning out of being here. Once he accepted that, he could be fully a part of the world, and then he could write “Rent.” I don’t think there’s an accident in that. That very visceral knowing of loss and of death, that’s what gives everything so much meaning. And without that awareness, we will succumb to meaninglessness.So what kind of meaning did this story give to you?Every frame, every moment, every breath of this film is an attempted honoring of Jon. And, on a more personal level, it’s an honoring of my mom. She is someone who showed me where I was supposed to go in my life. She set me on a path. We lost her just before Covid, just before we started shooting, after a long battle with pancreatic cancer. So, for me, I was able to continue her song on the ocean and the wave of Jonathan’s songs. It was an attempt to honor him in his unfinished song, and her in her unfinished song, and have them meet.I think that’s part of the reason I didn’t want this movie to end, because I got to put my grief into art, into this creative act. The privilege of my life has been being there for my mother, being the person that gave her permission when she was ready. We had a very amazing connection, and now an audience will know her spirit in an unconscious way through Jon, which I just find so magical and beautiful.“I’ve lost people before, but one’s mother is a different thing,” Garfield said, adding, “Nothing can prepare you for that kind of cataclysm.”Alana Paterson for The New York TimesStill, that’s a lot to deal with while you were shooting this movie. It can’t have been easy.I was hesitant whether I was going to share that, but I feel like it’s a universal experience. In the best-case scenario, we lose our parents and not the other way around, so I feel very lucky that I got to be with her while she was passing, and I got to read her favorite poems to her and take care of her and my dad and my brother. I’ve lost people before, but one’s mother is a different thing. It’s the person that gives you life no longer being here. Nothing can prepare you for that kind of cataclysm. For me, everything has changed: Where there was once a stream, there’s now a mountain; where there was once a volcano, there’s now a field. It’s a strange head trip.You put parts of yourself in other people, almost like they’re the stewards of who you are. And when you lose those people, suddenly you become their steward.As you say, it’s like my mother now lives in me in a way that maybe is even stronger than ever when she was incarnate. I feel her essence. For me, it only comes when one can accept the loss, and it’s so hard for us to do that in our culture because we’re not given the framework or the tools to. We’re told to be in delusion and denial of this universally binding thing that we’re all going to go through at some point, and it’s fascinating to me that this grand adventure of death is not honored.Actually, the only thing that gives any of this meaning is if we walk with death in the far corner of our left eye. That’s the only way that we are aware of being alive in this moment. I think that was the legacy that Jon leaves and the legacy that my mom leaves for me personally, is just to be here. Because you’re not going to be here for long.It reminds me of what was written on your script before all of this happened: “You don’t understand now, but you will.”“You don’t understand now, but you will.” I’m still reeling from the download of understanding what Jon’s life was about, what my mother’s life was about, what all of this is about. Oh God, how lucky to explore that in one’s work! More