Talking to Julian Slater, the sound man for "Baby Driver," is a lot of fun.

On the phone from his studio in LA, he mimics car engines and police sirens, merrily vrooming and woo-woo-wooing to explain how the Oscar-nominated film sounded so great.

The sound team's role in a movie is often unsung, but in "Baby Driver," music is the headline act. Writer and director Edgar Wright came up with the idea for a film in which the music and sound are at the heart of the experience, even replacing the script with an iPad app that played the relevant music as you read through it.

Wilson Webb

The job of tying the music and sound together fell to Slater, who previously worked on films such as "Mad Max: Fury Road" and all of Wright's prior movies, including "Shaun of the Dead" and "Hot Fuzz." For his efforts on "Baby Driver," Slater has been nominated for both best sound editing and best sound mixing (with Tim Cavagin and Mary H. Ellis) at the 2018 Academy Awards.

From the opening moments, it's clear "Baby Driver" is unique in terms of its use of music and sound. Not only does the titular getaway driver, Baby, live his life sound-tracked by the music he listens to, but the world around him dances to the same beat.

"In that first car chase sequence with the red Subaru WRX, all the police sirens are in time with the music," explains Slater, who worked as sound designer, rerecording mixer and supervising sound editor. "Regardless of whether it's a yelper siren or a wailer siren, all those are in time with the music -- as are the gunshots, as are the car revs. The sound for dog barks, cars, trains over train tracks, horns, they're all working in sympathy with the music at that particular point."

Noises made by things that appear on screen are called diegetic sounds (as opposed to nondiegetic sounds such as a film's musical score or a voice-over). Achieving the desired effect for "Baby Driver" meant approaching the sound design in a whole new way. "Normally in the UK we work in time code, and in America we work in frames," says Slater. "For 'Baby Driver' we work in bars and beats. Everything had to be broken down to musical notation."

That meant figuring out the tempo of each piece of music and making sure the other sounds matched that beat by stretching them out or speeding them up if necessary.

Things get complicated when we're hit with the ever-changing tempo of the Jon Spencer Blues Explosion song "Bellbottoms." "It's going one, two, three, four, one-two-three-four onetwothreefour, one, two, three, four," Slater explains, speeding up and slowing down to mimic the shifting beat throughout the length of the song. "Then you take, say, a police siren, and map the tempo of the siren to the tempo of the Jon Spencer Blues Explosion. You get a siren, rather than just going woo-woo-woo-woo-woo, it's going, woo woo woo woo woo-woo-woo-woo woowoowoowoo woo woo woo -- floating around all over the place."

Here's a video that shows how this works out in the film:

Now playing: Watch this: 'Baby Driver': Hear how the engines and sirens hit the...

Even the other music in the film matches what's going on in Baby's earbuds, like when he makes a getaway on foot and runs through a shopping mall where each store is playing its own music.

"You probably wouldn't have noticed this," says Slater, "but every time he goes into a shop, the music that's playing in the shop is synced to Hocus Pocus that he's listening to on his earbud. There's a rap track in the thrift shop that's rapping in tempo to the Hocus Pocus track."

That's the sound outside Baby's head. But we also go inside his head when he takes out the earbuds and we hear the ever-present tinnitus that afflicts him.

"Tinnitus is normally this high-pitched whistle sound you're used to hearing from 'Saving Private Ryan,'" says Slater, "but if you're gonna play it throughout the movie, very soon you realize that you're going to piss the audience off because it's just an annoying sound. So the tinnitus sound itself changes depending on the environment and how stressed Baby is."

The mixing of the sound also followed Baby's cue. Not only do we hear his tinnitus when he's not listening to music, but when he has only one earbud in, you hear music only on that side of the movie theater.

Julian Slater

Some sound is recorded on set, but for most films, background noises are re-created separately under controlled conditions. This is called "Foley," named after an influential sound engineer from the early days of cinema.

"We have someone who spends two to three weeks on a Foley stage who does all the footsteps and putting cups down and stuff," says Slater. But for this film, there were more exciting sounds to be recorded.

"We got onto a race track in Atlanta and re-recorded all those cars you see in the movie from every angle," he says. "We had microphones around the race track and we had a microphone on the exhaust, we had another microphone under the hood, we had a microphone on the driver's side, we had another microphone in the back so we had these multithread recordings of every single car."

Despite all those mics, there was still more work to do.

Slater admits he knows nothing about cars, but he does know sound -- and the race track recordings didn't sound quite right. "That red Subaru WRX has what's called a dump valve, so every time you rev it goes vrrrmm-tksshhh, vrrrmm-tksshhh. Which, if you're trying to syncopate stuff to music doesn't work, because you've got this tksshhh every time. So even though we recorded the Subaru WRX, very little of that was used. Hopefully the audience don't notice, but each car is an amalgam of say five or six different cars used in different ways."

Luckily, Slater and his team had a few advantages. First, they knew Wright had already decided on the songs. Usually, filmmakers will throw in temporary music while the final score is being composed, which means changes may have to be made late in the process. But with the songs already locked in place, Slater knew he could make decisions that wouldn't have to be changed later.

"I was literally two doors along from Edgar," he recalls, "and Edgar would come into my room months before the mix and we'd have a little play on one of the sequences, and he'd say to me, 'I like that but can we just turn that thing down?' I'd turn it down, and those fader moves followed all the way through to the final mix. Literally from day one you're building the final mix."

The other advantage is today's digital technology makes everything much quicker and easier. "My first job was working at a music library where I used to cut quarter-inch tape together," remembers Slater, "so I was lucky. I came in literally on the cusp of digital." Now he works on Macs running the music and sound-mixing software Pro Tools, utilizing different plug-ins for effects such as reverb or EQ.

With today's software, it's even possible to work anywhere. "You can mix a feature film in your front room if you like," Slater says. "But there's still something about sitting in a larger room and having the space between you and the speakers and the environment. If it's gonna be played in a large theater it makes sense to mix it in a larger environment."

This Sunday, Slater and "Baby Driver" go up against "Blade Runner 2049," "Dunkirk," "Star Wars: The Last Jedi" and "The Shape of Water" at the Oscars. The sound is such an integral part of the story in "Baby Driver" that Slater must be in with a chance.

"I wish I had everyone else's confidence," he laughs. "I've been lucky enough to get emails from my peers, people I don't necessarily know or haven't met, who've come out of the cinema and decided they want to contact me to say they really resonated with the work. That's a career highlight for me, and anything else after that is just golden."

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