Ray tracing, traffic lights, and howler monkeys – How Forza Horizon 5’s audio brings Mexico to life

Playground Games’ lead audio designer Fraser Strachan reveals Horizon’s secrets

Forza Horizon 5’s audio already made happy headlines last week as people discovered unlockable Banjo-Kazooie and Doom car horns but there’s far, far more to the sound of Mexico than just novelty noisables. Playground Games’ gear shift to a new continent meant that the soundscape changed entirely for the series. Not only that but a new, more powerful console also allowed for bigger changes under the hood that revolutionised the way simulated engine noise makes its way into our ears.

So get your foot on the gas, set your favourite radio station, and crank up the volume, it’s time to find out where that specific Forza feeling comes from. Spoiler: it’s the music. The impressive vistas are a key indicator of a fresh new sprawling country to explore but to fully feel like we’re a part of Forza’s race festival, the choice of music on the radio is the vital source of that celebratory feeling. And that means Playground Games audio team effectively has to become music festival planners. Thankfully without worrying about Fyre Festival-style cheese sandwiches.

“The Horizon Festival is a car and music festival, but it’s also a touring festival which comes with its own kind of culture,” explains lead audio designer Fraser Strachan. “People expect there to be big well-known names as part of the festival that potentially would be people who have come to visit the country. So when we’re when we’re looking at a location such as Mexico, we’re looking at which artists are popular within that region, who would be the touring headline acts anyway to come and visit that country, as well as making sure that we’re representing local artists and featuring not just top tier artists, but those middle names and the smaller names on the festival posters.”

Forza Horizon 5 screenshot
Forza Horizon 5. Credit: Playground Games

Strachan and the team went deep into grassroots areas, hunting for up-and-coming artists across Mexico to ‘introduce’ with the Horizon Festival and get onto our car radios. They also worked with Mexican artists to write music specifically for the game. As well as the more modern pop element, there’s a classical station, Radio Eterna, playing pieces from Mexican classical composers like Juventino Rosas. This orchestral option is something that has become more important for Forza as a whole. “I think this is the first game that we’ve actually tried to move into that more cinematic space because we’ve got far more gameplay experiences that suit that sort of style that needed bespoke music for it,” explains Strachan.

“It was an interesting thing to think of. ‘What does the Horizon Festival sound like mixed with classical cinematic music that also has to be authentic to Mexico?’ There’s one experience in particular called the Tulum Expedition where we worked with a composer from the UK called Ian Livingstone, who’s got a lot of contacts in the region to figure out what types of instruments to use. He worked on this piece with us to write something that was very orchestral, but had a sense of synths in the background. It had live drums in it to really blend this modern sound with orchestral.”

The magic of Forza 5’s radio stations is that you always feel like you have the choice to play with exactly the soundtrack you want. Regardless of what you turn on though, it always has to deliver one key feeling for the dev team. “I think a lot of people would think it’s fairly easy to pull together an indie station and a bass heavy station and a classical station, but throughout all of them we have this DNA,” confirms Strachan. “We always listen to something and we’re always asking, ‘Does it feel like it’s Horizon?’ Because Horizon by now, we’re on the fifth game and it has its own vibe that comes with it. And for us, that’s a very happy feeling. It’s that sense of wonderment and living your best life and if a song doesn’t evoke that emotion in you, then it might not be suitable for the game.”

Forza Horizon 5
Forza Horizon 5. Credit: Playground Games

And while, yes you do always have a choice of what to listen to, you’re still playing with a carefully constructed soundtrack for exactly where you are in Mexico and what you’re up to. “In most of the events that you can play for the first couple of hours of the game we actually choose a music track from each of the radio stations that suits the vibe of those races,” Strachan explains.

“So if it’s a race in a dust storm, then we’ll pick something that’s kind of dark and moody, but from each of the genres so that if you’re someone who listens to hip hop, for instance, then you have something that suits your style. The Expeditions is probably the one example where we actually lock some of the radio stations away. We almost mask that you’ve got this radio station going on and you’re listening to the piece that we’ve written for that.”

The good news is if you don’t like it, you can always switch it off and the radio will always remember what you were listening to before the mission and switch you back to your frequency of choice. There are also carefully cultivated playlists for the occasions when you’re out and about between events and the music will switch to a free-roam option just to make sure you feel as adventure hungry as possible.

But while music is a key element of Forza’s soundscape, Mexico itself is the star here. Whether you’re screeching through cities or splashing through lush jungles, everything sounds intensely alive. The team didn’t manage to make it inside an active volcano with their mics (“health and safety kind of gets a little bit in the way of that”) but they did travel all across Mexico recording the ambient sounds of deserts and cities. On top of the regular sounds like bird noises for aural signposting to know where we are, Strachan highlights traffic light noise as being very region-specific. But one of the team’s unique revelations was primate-based.

Forza Horizon 5
Forza Horizon 5. Credit: Playground Games.

“Do you know the one that really took me by surprise was the howler monkeys,” Strachan laughs. “Something that we found really interesting was that howler monkeys… they don’t really like cars very much. They shout at them quite a lot. Some of the best ways to get the howler monkeys to make sound was whenever the cars were driving past, they would set off and you’d get some really good recordings. We decided, ‘wouldn’t it be really cool to implement that in the racing game in the same way?’ We had this system where we can use crowd excitement values. So in the festival, if you’re doing donuts or you’re driving fast, the crowd will be cheering in reaction to your car. We’re using those same parameter values actually to drive the howler monkeys in the jungle. So it’s funny to think of the howler monkeys being an excitable crowd in reaction to your car that you’re driving.”

One of the biggest and noisiest new additions to the series is the extreme weather. Mexico’s tropical storms and dust storms come with their own unique challenges, not just for driving in but for recreating as an aural assault. “The creative director was saying to me, ‘What does a dust storm actually sound like? Is it just like being in a snowstorm or fog? Like, does it dull the senses?’, explains Strachan. “So we actually use a lot of references. I don’t know if you’ve seen Interstellar, but there’s a great audio feature that they pulled together where they had this sand blasting machine blowing dirt and debris against the vehicles as they’re driving them through these dust storms. And really, it was all about the kick up and the stones and all that stuff that’s getting chucked at your car. So it’s not necessarily the sound of the weather swirling around you. It’s how you, as a player, interact with the debris that is being chucked around.”

Forza Horizon 5
Forza Horizon 5. Credit: Playground Games.

And that audio changes as we switch cameras between the driving seat and something a little more zoomed out, meaning that the team has to deliver a full storm experience. “When you actually play inside the cockpit of your car, this means we change all the sounds completely. You’ve got your surround sound debris on glass, but you’re also hearing it on the metal above you in the cabin. It’s quite an intensive system that we’ve done,” he explains.

The tropical storms too are a step up from the rain of previous games, meaning that you’re under serious assault from the skies. The relatability of driving in intense rain was something that the team had to think about recreating in Dolby Atmos too. We’ve all sat in a car park listening to the rain thunder down and wonder if we should turn the key. “It’s something that we did spend a lot of time trying to get right because it is something that a lot of people would know if it wasn’t right at all,” confirms Strachan. “There’s one of the gameplay experiences where you drive underneath a waterfall and we spent a long time making sure you could hear that transition of the waterfall from the front to the back of the vehicle. And the reason for that was most people have been through a drive through car wash! They know they probably know what that sensation of a shifting audio sound all the way across your car is. Whereby most people don’t know what it’s like to stand normally in the middle of a dust storm…”

Then there’s the small matter of ray tracing being used to bring Forza’s engine audio to life in an authentic way. If you thought it was just for shiny puddles, think again. “When we started Horizon 5, we really wanted to figure out a way to make the car feel like it was really rooted in the environment. You can’t really have a loud modified car without thinking about how in real life you hear that four blocks away and you hear it slapping off all the buildings, and we wanted to really replicate that,” explains Strachan.

Forza Horizon 5 Bronco
Forza Horizon 5. Credit: Playground Games

Premade systems weren’t working as they just weren’t fast enough to update in real time so the team used ray tracing to map the audio across Mexico. “It was the obvious choice for us. You’re constantly sending out information from where your player car is. Essentially, we’ve broken it up into multiple surround sound directions. So we’re sending off rays front left and front right, back left and back right to match that surround sound speaker configuration that you would get if you’re playing in 7:1,” he explains. “And for each one of those that we fire out, those rays, they’re essentially looking for a wall or some other type of material. And when it finds it, it will go, ‘Oh, I can tell that that’s concrete. It took me x number of seconds to reach that wall.’ It’s using the speed of sound. And then what it’s doing is it’s saying, ‘well, it’s concrete so that’s a very reflective material so let’s send back the full signal.’ Basically you get your initial delays based on the speed of sound and the amount of sound that’s reflected back is based on what material you hit.”

Finally, the even better news is that you don’t need a 7:1 surround sound system to truly appreciate Horizon 5’s audio extravaganza. “I think honestly, a lot of people would expect me to say, you need to have a full 7.1 surround sound setup,” smiles Strachan. “But I think as long as somebody’s got a really decent pair of stereo headphones, I think that’s the best way that you can experience it. You know, even a nice pair of stereo speakers at home, you’re going to be fine. The interesting thing about this game is that because of the transition to work from home and lots of other reasons like that, we’ve actually mixed the game in far more endpoints than we ever have done before. We’ve been listening to the game on headphones, we’ve been listening to the game on soundbars, we’ve been listening to the game probably on more different types of platform than we ever had access to before because we were at home. And for that reason, I actually think this game sounds the best that it’s ever done on, whether it’s bog-standard earbuds or high-quality Dolby Atmos theatre systems. So yeah, as long as you’ve got a good pair of headphones, that would make me happy.” Go on, make Fraser Strachan happy. You know you want to.

Forza Horizon 5 is out now.

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