Every now and again, a movie trailer comes along that really grabs your attention. It’s not just the visuals that flash by on-screen or the actors that make it stick in your head — it’s the music. More often than not, it’s music that’s been commissioned for the trailer, composed by people like Frederick Lloyd. Over the last couple of years, he’s been responsible for the trailer music for some of Hollywood’s biggest films.

You’ve probably heard his work without knowing it: his music is featured in trailers for Mad Max: Fury Road, Alien: Covenant, Star Wars: The Force Awakens, and Star Wars: The Last Jedi, just to name a few.

Lloyd explains that he fell into composing trailer music by happy accident, and that his goal was — and remains — to become a film director. He began to dabble in composing music when he attended film school in 2009, and came up with his current moniker, Ursine Vulpine. It was while at school that he began to compose the soundtracks for his own films. “I said, ‘Okay, this is something else I can do,’ and when it came to my graduation film, Pantheon,” he tells The Verge, “I had this soundtrack.”

Through some contacts with his managers, the soundtrack for Pantheon made its way to Los Angeles, where one of his tracks, “Decompression Reborn,” was used in a trailer for Katheryn Bigelow’s film Zero Dark Thirty.

“That’s why this kind of blew my mind a little bit, and I thought at that point that maybe this is something I can do,” he says. From there, he went on to help with the music for a trailer for The Force Awakens, and last year, reworked The Flaming Lips’ song “Do You Realize??” for the first trailer for Transformers: The Last Knight.

Each trailer is slightly different, he explains, but generally, each track comes about in two different ways: he’s either given a brief, which outlines what the trailer’s editors are looking for, or he comes up with music on his own.

In each case, he tries to pinpoint what the broad themes are that he wants to convey to the audience, whether through atmosphere, mood, or pace. Usually, he starts with a single note and creates a structure around it, building and fleshing out the music. “It evolves very naturally,” he says. “It’s always been a very instinctual process for me.” Most of the music that he puts together is done electronically, but he does use live strings, a guitar, and sometimes, live vocals. He says that he has yet to use a live orchestra for any of his music, give the cost and time constraints that usually come with each project.

The trailer world isn’t immune to trends. When the first trailer for Christopher Nolan’s film Inception hit in 2010, it immediately attracted attention for the deep bass brwaaaaaaa that drones its way through the trailer, something that was immediately picked up by a number of other trailers that followed it. Lloyd notes that the trend of the moment is a haunting, slowed-down cover of a popular song, and that he’s made a couple himself. Keeping his music fresh, he explains, means “interpreting those trends and trying to do something slightly different with them.” Doing a cover is all well and good, he says, but “it’s about what you do with that cover that’s different from everything else.”

Lloyd says that he doesn’t usually have any input into how a trailer is edited, and he doesn't generally see the finished product before he begins composing. Once he delivers the song to the editors, they’ll often shape the trailer around what they’ve been given, which means the trailer might be edited to fit the music, or the music might be molded to fit the footage. “It’s very flexible on either end,” he explains. “I’ll get notes back about things that they want to change or tweak, and I’ll do that.”

When asked about what the next big trend would be, he says he isn’t sure, but thinks that he and the people he typically works with are ahead of the curve. The first cover that he put together for a trailer was back in 2013, which recently ended up on the first Transformers: The Last Knight trailer. “If I knew [what the next big thing is], I’d probably be very rich,” he laughs. “It’s a hard one to pin down, but I’m hoping that it’s a lean toward original work.”

Earlier this month, Lloyd released a short film and accompanying album called Respire, a retrospective of his career thus far, which features many of the songs that have ended up in trailers over the years, such as Mad Max: Fury Road and The Hunger Games. He says the track list is roughly in chronological order, with some of the earlier tracks “spruced up a bit, because they didn’t particularly match up well” with some of his later tracks.

Since he began down this path, there’s been quite a few changes to how he approaches his music. He observes that he’s expanded beyond the acoustic guitar that he started with, to use “a more cinematic sound,” and recognizes that, while trends in trailer music shift, the end goal remains the same: a track that builds to become something bigger by the end.