Behind the Spirited Sound of ‘Slow Horses’ – with Joe Beal and Martin Jensen

Mistakes have been made; careers have suffered. For those MI5 misfits that just don’t make the grade, their destination is Slough House. The Apple TV+ series Slow Horses tells the comedic tale of these well-intentioned yet inept agents, led by the irreverent Jackson Lamb (played by Gary Oldman). The show, which just finished its third season, has earned several BAFTA TV Award nominations, including one for “Sound: Fiction.”

The sound of the show blends comedy with action. In the quieter moments, sound reinforces the character’s flaws – like Lamb’s flatulence – or undermines their aptitude as agents, or reminds the audience that Slough House is a dumping ground. Its creaky floors and shabby office furniture befit the status of the occupants. The action-packed shootout scenes lend a sense of jeopardy – will these incompetent MI5 operatives actually win the day? And when they do, you’re kinda with them. Flawed as they are, there’s something appealing about the underdogs.

Here, Boom Post supervising sound editor Joe Beal (Emmy Award-winner for sound editing on HBO’s Chernobyl) and re-recording mixer Martin Jensen (winner of a BAFTA Film Award for Best Sound on The King’s Speech, a BAFTA TV Craft Award for Sound: Fiction on Netflix’s The Crown, and an Emmy Award for sound mixing on HBO’s Generation Kill) talk about the evolution of the sound across the three seasons of Slow Horses, how they use sound to support the comedy and action and set the tone of Slough House, how sound helps reinforce each character’s flaws and quirks, and how they handle the big action moments in a comedic way. They also dive into details for specific moments in Season 3, including the shootout in Ep. 5 and Ep. 6, and more!

Slow Horses — Season 3 Official Trailer | Apple TV+

Since you worked on all three seasons of Slow Horses, can you talk about the sonic evolution of the show? In what ways do you try to improve the sound of the show each season, to build on what you’ve done previously? Also, how do you keep the essence of the show’s core, and adapt that to each new scenario?

Joe Beal (JB): It was clear when we started on Season 1 that the success of the show as a whole was going to be based on two things: the delicate balance of comedy and action, and the really strong characters.

The tone of the show balances on a tightrope the whole way through and we knew that we would have to follow suit with sound. We have to balance our editorial ethos between being strong and exciting with our action sequences and funny when necessary. Sometimes those two things will live quite separately scene by scene, but often it’ll be a case of following the tone in the script and performances closely and shifting the soundscape subtly and quickly within a scene.

We have to balance our editorial ethos between being strong and exciting with our action sequences and funny when necessary.

The show is also very character-driven; Gary Oldman as Jackson Lamb, Jack Lowden as River Cartwright and generally all of the Slow Horses have really strong personalities. We wanted to develop how they interact with the world. So for example when Lamb slams a door, it would read differently from when Standish does. Developing those character traits, as well as building up the world around them, has been a big process.

We’ve tried to treat the two MI5 locations as characters. In Slough House, everything creaks or groans or buzzes or drips. That’s set in contrast to The Park, where everything has a sleek swoosh, modern beep, or chunky clunk. It’s been great fun establishing and developing those ideas.

We’ve tried to treat the two MI5 locations as characters.

I suppose the evolution of the sound of the show has been around grabbing onto those core principles, establishing them strongly, and then applying them to each situation that we find ourselves in. The specifics of that can be quite varied. Building interesting character traits and knowing that we’ve established these conventions strongly early on means that we can now lean into them harder for comedic effect. Then when we need to balance that with dramatic action sequences – when the Slow Horses need to seem like sleek spies – it’s enhanced because of the contrast. The guns really do punch through, and the Range Rovers really do screech around.

Martin Jensen (MJ): We try support the comedy with particular sound effects. If a chair creaks, it always creaks a little bit louder in Slough House than you’d normally play it elsewhere. We try to push it as much as we can. There’s a lot of that going on at Slough House.

 

Talking about supporting the characters through comedy, Jackson Lamb is quite flatulent. Is there a fart library that was really useful for the show? Did you have Gary Oldman come in and perform a few for you?

JB: Gary, unfortunately, wasn’t available to perform his farts for us… But our fart sound library is pretty extensive from years of dedicated recording by the experts here at Boom!

No, honestly, we’ve done a few projects over the years that have required a variety of farts. We worked on an adaptation of Fungus the Bogeyman years ago which required a pretty thorough library of that kind of thing, so that was my starting point. Plus we’ve got 20+ years of material in our internal library from immature sound editors with easy access to microphones, so we’ve got a fair bit of flatulent material there.

…our Boom effects library consists mostly of bespoke recordings from our team of editors.

It raises a more serious point though – our Boom effects library consists mostly of bespoke recordings from our team of editors. One of our big successes here, I think, is how broad our library is and how dedicated everybody is to carrying around a recorder in their backpack and catching things on the fly, or getting out into the field on each project we do and recording new material. Often, it’s more serious things than farts, but sometimes they’re included too…

MJ: A lot of the sound we create here is done with our own recordings and we do feel very much that’s what helps to set us apart.

JB: We’ve shot lots of material for Slow Horses over the three seasons. I’ve got quite a good track record of booking holidays to places that then come up in shows or films that I’m working on a few months later. I happened to be going to Istanbul, so when we saw the opening of Season 3 that had a car chase through the city, I realized it was a brilliant opportunity to take my recorder and grab some sounds. I’d already seen the opening and so was able to get into the right places and get some great atmosphere sounds and some specifics to drop in. The call to prayers, the traffic noises, the market sounds, and the general sense of Istanbul are all our own recordings. It amplifies the show and lets us put our personal stamp on it.

The same goes for the sound of London. In the first season, we had the brief to make London feel grungy and alive, so we got out and about to catch the life of the city. The most useful recordings are the bespoke atmospheric moments that we can poke through our scenes – buses, horns bouncing off the tall buildings, weird alarms, shutters clanging shut, and people shouting on the street. I got told off by security guards in the City of London just opposite Slough House for trying to hide in a corridor and record interior traffic sounds.

 

So, you’re standing across the street from Slough House (where the MI5 office is in the show) and recording? Did you get patted down?

JB: No! It’s not really MI5… In the show, the exterior of Slough House has this Italian restaurant beneath it and the offices are at the top. The location is really in what’s called the City of London – a square mile in East Central London. They have their own local authority and Police and the City owns a lot of the buildings.

I went there to record and saw an open doorway opposite Slough House and thought it was a great opportunity to get some ambient street sounds. It was right next to a big road so I could get rumbly corridor sounds for Slough House, but this chap in a white shirt with red and white checks on it and an official-looking hat came and told me off, and told me that I wasn’t allowed to film. I did try to explain that I wasn’t technically filming, but he didn’t want to hear it.

 

Now that you’re in Season 3, you’ve settled into a groove and know what to expect from the showrunners – what their tastes are and what the builds for each show are going to be. How have you been able to improve the sound of the show with that knowledge that you now have?

JB: The crew on the show is brilliant. We have a great relationship with Seesaw, Apple, and our execs, producers, and directors – everyone really. We’re all pulling in the same direction and I think it shows on screen. James Hawes, our Season 1 director, pushed us to establish the world strongly and the team went with it. At the beginning, the expectation was that it would be quite funny and we pushed the boat out. Now, they expect it to be really out there and we can keep building on it. They seem to be on the journey with us and happy for us to go for it, especially in the comedic moments.

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It’s been great fun to double down with where we wanted to take the sound of the show and the wider production team has been supportive the whole way. So much so that Apple trailed Season 2 with a series of short clips with just our foley and FX sounds on them. It was nice to see that our work was really giving something to the atmosphere of the show, as often those details can fly under the radar.

 

Let’s talk about some of those character sounds. Are those mostly foley-driven, or did you also build up an effects library of signature character sounds?

JB: It’s a combination of the two. Our Foley Artist, Catherine Thomas, is absolutely brilliant. She’s got a great ear for detail that will cut through a busy mix and we often support her with FX.

Our Foley Artist, Catherine Thomas, is absolutely brilliant.

Lamb’s shoes from Season 2 were a good example. There were a few close-ups of him kicking his shoes off and they’re mangy, old, leathery, creaky things. Off the cuff, our director said, “It’ll be good if his shoe squeaks.” So for the remaining four episodes of that season, we had a combination of effects and foley work in there of his shoes creaking wherever he went.

Martin also did a lot of mix work for the car, amping it up, and making it feel like there’s a big stupid subwoofer in there…

The same goes for all the Slough House crashing and banging really. Whenever Lamb slams a drawer or thumps something down on the desk, it’s usually a combination of FX and foley. Cat will give us some detail and a nice bespoke element that we can embellish or add to with FX if we need to. We’re taking the foley and wrapping it into our Spot FX pass so that we know everything is as embellished as fully as it can be by the time we get to the premix.

Roddy always gives us opportunities in the FX world. We see his car for the first time in Season 3. He’s got a throwback boy racer Subaru which looks ridiculous, so it had to sound ridiculous. We managed to hunt down some over-the-top recordings of the original car and we created sounds for this silly character animation on his car’s touchscreen.

Martin also did a lot of mix work for the car, amping it up, and making it feel like there’s a big stupid subwoofer in there when we hear anything through its speakers.

 

There’s a great scene with Roddy sitting in the car, waiting for Jackson, and he’s singing along to a song about Alexander the Great. How did you handle that?

JB: The dialogue was all production sound. He had an earpiece in and was singing along to the song. It was shot without music but it synced up nicely because he had it playing back in his ear.

Martin did a brilliant job of pushing into the music quite subtly and shifting the perspective as we approach the car.

Roddy has a great voice; we’ve been told that he’s a keen singer! It was an interesting shot because the camera is outside the car quite far away and it slowly creeps forward. You need to feel the distance between you and him at the beginning – you really want to feel the ridiculousness of him sitting alone on this quiet lane pumping out Iron Maiden. As the camera pushes in, it needs to transition to feel like you’re right with him in his energetic singing. Martin did a brilliant job of pushing into the music quite subtly and shifting the perspective as we approach the car.

MJ: As Joe was saying, Roddy has this ridiculous voice for the car that comes through the stereo system whenever the car turns on and off. So, we had to decide what kind of audio system he would have in his car. He’s probably got a subwoofer that has lots of bass. So, we’re trying to make the track sound as it would in this car with a bass-heavy speaker system – to make it as ridiculous as we could.

 

For the transitions between the comedic and action moments, how do you support those with sound? How do you make those live in the same Slow Horses world?

JB: They can be quite subtle things and it’s about picking them out where you can. It’s a judgment call in each scenario as to when and how far you go with it. In Season 3, there’s a chase scene through The Park with River and “The Dogs” (MI5’s Internal Tactical Unit). River jumps off the bridge and you hear a slightly gratuitous crunching sound as he hurts his ankle when he lands. This scene is all systems go – loud music, shouting, etc. – and all of a sudden we’re trying to pick out the detail of his limping footsteps to push the comedy rather than drive the action forward as you might usually.

… subtle comedy had to cut through some quite heated action.

There’s a similar thought process in the warehouse shootout scenes in Ep. 6. Marcus and Shirley are hiding from the Chieftain operatives who are shooting at them in a huge warehouse. It’s another place where subtle comedy had to cut through some quite heated action. The Chieftain soldiers are shooting from such a distance that you can play up the time differences between the shot and the bullet impacts. The bullets whiz in and ricochet off the metal and concrete just above them, and we pick up the close detail of the debris that’s raining down on them. It’s cut from their perspective, with wide, distant guns but close detailed ricos and debris. Being shot at by a sniper rifle isn’t funny, but screaming and shouting in a stupid way while the dust rains down on you is. Taking those perspectives into account at the editorial stage and thinking about how to approach the scene reinforced the comedy of the situation and gave Martin a starting point to enhance on the mix stage.

Often the comedy comes through a little look that one of the characters will give or a little stumble that they might have, especially in Slough House. They might have a heavy conversation about something terrible that’s happened, but they’ll walk away and the floorboard will creak. It can add that bit of levity into a serious scene and help balance the overall tone of the show.

 

Let’s talk about that big shootout in Ep. 5 at the MI5 storage facility. What were some challenges and opportunities for sound there?

JB: The challenge was trying to balance the character-driven comedy sounds but have it feel really dangerous and action-driven. We wanted our guns to be huge and we wanted to give a good sense of the geography of the small green room. Saul Metzstein (Season 3 director) shot it brilliantly; it’s all tight shots that cut around to different perspectives in the small room.

We try to treat it like a drum kit, getting the rhythmic and frequency variation in there…

When it all kicks off, editorially we hear everything quite distinctly. We’ve got gun mechanisms and firing that vary with perspectives, bullet whizzes and ricochets, ADR breaths and reactions. We try to treat it like a drum kit, getting the rhythmic and frequency variation in there so it makes sense around the dialogue and lands in a satisfying way. We have big ricochets on every bullet hit, and we fly them around the room depending on perspectives. It’s a combination of us creating space in the FX and cutting cleverly around dialogue to give enough room in the mix for things to move around and give a good sense of the offscreen action. When we expanded it into the scenes in the bigger warehouse room, we were able to draw on those ideas even more.

MJ: We had a lot of fun in the big room because we could use massive reverbs and play the guns as big as we possibly can and play with perspectives. It’s a very fun sequence to do because we’re trying to make the effects stand out while still being able to follow the dialogue.

Editorially, there are beeps for the number keys and those rise in pitch quite subtly, trying to amp it up and be slightly funnier…

JB: There were subtle sounds in there as well, in the build-up to the shootout sequence. When River and Douglas (the manager of the facility) are trying to type in the override code so the door won’t unlock and let the Chieftain operatives in. Editorially, there are beeps for the number keys and those rise in pitch quite subtly, trying to amp it up and be slightly funnier than you might be with it.

Mix-wise, we’re pushing them slightly louder than you would on another show. So, there’s this quite dramatic, stupid conversation happening but there is work going on in the background to ramp things up.

MJ: And that happens with the dialogue and music, those go up as we’re trying to make the moment more and more dramatic. It might be subtle, but it has a great effect.

 

What about the dialogue challenges in this location? It seems like a reverberant space. Was that an issue in terms of production sound?

MJ: Andrew Sissons, the sound recordist, did a brilliant job, and we are also blessed with some new tools that helped us in terms of noise reduction.

When you can use a lot of reverb, it’s almost easier sometimes, certainly from a mix perspective.

And, because it’s in a big space, we can use a lot of reverb. That helps the geography, whether you’re close to a character or a bit further away. When you can use a lot of reverb, it’s almost easier sometimes, certainly from a mix perspective. The challenge is to not overdo it because then you start to lose intelligibility. So it’s a balance of not overdoing the reverb, but having enough on there to move the characters around in the space.

JB: The shootouts in Ep. 5 and 6 were shot using loud blanks so there was a lot of compromised dialogue. Our dialogue editor Duncan Price is brilliant, and along with the cast, did an amazing job of injecting energy into ADR performances. What you hear in the final mix is a real mixture of sync dialogue and ADR – as so often happens.

We shot a lot of breaths and efforts which allowed us to pull perspectives really abruptly.

ADR was really helpful in the green room shootout scenes too. We shot a lot of breaths and efforts which allowed us to pull perspectives really abruptly. You’re in a tight space with bullets whizzing past and suddenly you shift perspective from a bullet that’s just hit something on the left to your character standing on the right. Having closely edited, well-recorded, and well-performed ADR available was completely invaluable for that.

 

The dialogue on the show sounds fantastic, especially since it’s shot in so many different places, like out on the street, inside car interiors, inside different restaurants and cafes, out in fields, and everywhere else…

JB: Martin and I were talking earlier about how much we gain from it having been a continuous team. The production sound team headed up by Andrew is fantastic. They have a good understanding of what we get up to in post and we know exactly what we’re going to get from them. It just makes everything much smoother.

Having continuity has allowed us to establish trust and a workflow which gives us great results

Duncan Price (DX Editor), Martin (Re-recording Mixer), Cat (Foley Artist), myself (Supervising Sound Editor), as well as our Studio manager Nicky Poulton and our post supervisors and coordinators have been across the whole series so far. Having continuity has allowed us to establish trust and a workflow which gives us great results. Nothing is changing and upsetting it too much which leaves us time to manage new challenges we face from set. So we’re in a really good spot; we’re happy with what we’re producing in terms of a dialogue sound and we can continue that with a consistent team.

We have a good workflow so we can spend time doing what it is that we love doing.

MJ: That’s something that’s coming from the first season when we were finding our feet with it on all levels. Because we’ve all been able to carry on, we’re not spending time on logistics and how to do stuff. It’s more about doing the work rather than working out how to accommodate everyone’s way of working. We have a good workflow so we can spend time doing what it is that we love doing.
 

Ep. 6, the season finale, is the most action-packed episode. What are some of your standout moments for sound in this episode?

JB: The action sequence at the end of Ep. 6 was really fun. It allowed us to apply all the things that we’ve spoken about in terms of comedy and action. It’s an intense sequence with people getting shot, stabbed, and killed in all sorts of ways!

We got everything sounding punchy. Then we went through and picked our moments where we could add in a tiny bit of comedy…

We went through it and did a close, dramatic, impactful pass in terms of FX editorial. We got everything sounding punchy. Then we went through and picked our moments where we could add in a tiny bit of comedy – changing the tonality of a ricochet to make it slightly funnier, having a door chime sound for when Shirley opens the door to the Nissan, having the grenade bounce off the sides of the shaft about six or seven times when Shirley throws it down into the bunker. It’s just finding those little moments where we can inject a bit of humor.

MJ: The mix and the editing are interconnected. I’m going through it frame by frame, trying to find somewhere we can make the cut sharper, or enhance the comedy, or make things more dynamic. Making it dynamic is probably the main thing, so that it’s not flat – we don’t want it to be mushy and boring. We’re always trying to find something to grab hold of sound-wise.

JB: There’s also a big music cue that runs through it. Going back to the consistency point from earlier, we can do more in the time that we have because the music is always consistent. We’ve worked with the composers for three seasons now. The music drives everything forward in a way that we’ve come to expect, and it’s about finding space around it and complimenting it.

…we can do more in the time that we have because the music is always consistent.

MJ: We’re also working with the music as stems. For a sequence like the shootout, we might end up with a synth pad that eats up a lot of sonic space and we need to determine what we want to make space for – such as the guns. We might lose a stem from the music (a synth pad or distorted guitar, etc.) if that gets in the way. The propulsive drums can carry the beat of the scene, so we may focus on that. It’s all about focus – what needs to take priority at the moment? And often in an action sequence, you try to go with the propulsion of the music rather than perhaps the tonality of it.

 

What scene in Ep. 6 went through the most iterations mix-wise? What were some of the options you tried in the mix, and what did you ultimately land on – what worked the best?

MJ: Dialogue is king for the show because it’s a comedy. We need to land every single line. A fair bit of time in the mix is spent making sure that we don’t have a cup being set down at the same time as somebody saying an important line, or there’s a gunshot on top of it. We try to dig things out and make sure that if an actor trails off at the end you can hear what’s being said. So a fair bit of time in the mix is spent refining the dialogue and making sure nothing is lost.

Because the show is so character-based, there’s so much nuance and subtlety in the performances.

JB: Because the show is so character-based, there’s so much nuance and subtlety in the performances. There’s so much you can add by really being meticulous with the sync. So, for instance, when Lamb is eating, it’s disgusting. We can foley it or put effects on it, but so often the really tangibly gross stuff comes from picking through the sync and cutting it in a smart way to focus in on what Gary has performed.

Gary Oldman and Jack Lowden ultimately set the standard for the show that we’re constantly trying to match. Both of them are brilliant and we work off their performances massively. Our cues for how far to take the FX and foley work are often taken from their body language and how far they’ve taken their performances.

 

What format is the show mixed in, and where do you mix it?

MJ: It’s mixed in Dolby Atmos here at Boom Post in Soho, London. We’re constantly referencing a stereo fold-down on a TV in the studio, and usually, we’ll do a final listen-through on that. We’re also listening back on Apple Airpod Max headphones too, as that’s generally what our Apple execs review on. You hear a lot of detail on the headphones that get lost on the TV. The mix we produce needs to work on your home Atmos setup, it needs to work on built-in TV speakers, and it needs to work on headphones. It needs to work on a lot of different platforms, even on an iPad or phone. But we only do one mix and that’s the challenge – to make a mix that works across all different devices.

You don’t know how your mix is going to be played back, and so you have to make strong editorial decisions to force your point.

JB: It’s certainly something I think about editorially – how things are going to be played back and how best to drive home your point. For example, you can’t be sure that by turning the low exterior traffic hum in Slough House up by three decibels that it’s going to play back and register as such on all devices, and that people are going to understand that it’s a really loud and crappy place. But if you put in a pokey car horn as you cut in, or a bus going past that rattles the building, you can be sure that’s going to translate and people will get the idea. You don’t know how your mix is going to be played back, and so you have to make strong editorial decisions to force your point.

 

A big thanks to Joe Beal and Martin Jensen for giving us a behind-the-scenes look at the sound of Slow Horses and to Jennifer Walden for the interview!

 

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