Brazilian cinema flowered intensely during the 1960s, but relapsed into comparative obscurity until 1999, when Walter Salles’s poignant and compelling Central Station won awards around the world. Salles had already caught the eye of film buffs at the Sundance Festival with his earlier film, Foreign Land (1996), and he pursued his career with Behind the Sun (2001), and The Motorcycle Diaries (2004). This film, based on the early life of Che Guevara, has proved a huge success wherever it has been screened, and won the BAFTA Award for Best Foreign-language Film, the Academy Award for Best Original Song, and a fistful of other prizes.

Quietly self-confident, extremely articulate, Walter Salles has inspired a generation of Latin-American film-makers, and has served as executive producer on City of God (2002), which reinforced the image of Brazilian cinema in Europe and the U.S. he also knows more film history than most university professors.

"Jean-Luc Godard was the one who opened my eyes to the importance of sound in the sense that he did not treat sound as it was in all other films. With Godard, sound was never in full synchronicity with the image. But it furnished an additional layer of understanding. That’s when I realised that sound did have a very powerful narrative potential. In my films, the first time when I managed to apply that concept, or rather find a concept that would work for me, was in Central Station.

"Central Station is the story of two people who get their identities back, and the film starts in the chaos of a train station in Brazil. Little by little, the narrative drifts towards the interior of the country where one of the two characters – a young boy – is striving to find his father. In thinking about that film, we soon realised that sound design could add a lot to the perception the spectator would have of the story, in the sense that we needed to convey the chaos in that station, we needed to use sound to show that that was the starting point – the space of lost identity, the space where people were just numbers, part of a mass. Gradually, as they move further and further away from that environment, they can understand much better the world that surrounds them. This prompted us to work with 25 or 30 different layers of sound in the station.

"And the further the story penetrates into the heart of the country, the closer and closer you get to the boy’s hypothetical father, the more defined these layers of sound become, and the more specific they get. We started to search for sounds that would have more ‘focus,’ that were actually definable, whereas in the station you have the noise of the trains, the loudspeakers, the echo of conversations of hundreds and hundreds of people, and then you have the voices of those characters who are dictating their letters to this woman who takes notes for them and "posts" them off.

"All these layers add to one another and sometimes they collide with one another. The further you go across the country, the fewer layers we use and the more defined the layers become. For example, you could very distinctly hear a dog barking now. You could hear a child sing something in the background. We clearly diminished the layers when we wanted to show that the characters were recuperating their understanding of the world around them.

"So sound played a very important part in defining the concept of the film. Every step of the way, it went in synchronicity with the image, because at the beginning there’s very little depth of focus in the image and as you go closer and closer to the hypothetical father, we used more and more depth of field. Therefore it’s about being able for the first time to listen and see the world surrounding those characters. For a piece of music to be interesting, it cannot be monochromatic. It must travel a little bit within that theme, and that is what we tried to achieve in Central Station."

Did he shoot a lot of wild track, I wondered? "A lot in the station, yes, in a very peculiar manner, because we didn’t want the people to perceive that we were recording either image or sound. Most of the time there was just one technician with a small Nagra doing the recording, holding his own mike, and the camera was hidden 70% of the time we were shooting inside the station."

In Behind the Sun, there’s a marvellous chase sequence where Salles emphasises the sound of the panting of two men as one pursues the other through the scrubland. "I tried to edit that sound with and without the music," notes Salles, "and the direct sound was far more effective than any musical piece in that film, showing that sometimes there’s nothing more expressive than direct sound."

Five years later, when Walter Salles made The Motorcycle Diaries, progress in sound technology had made significant strides, with digital coming to be the norm. The director laughs. "You’d be surprised to know that we also used an old Nagra for The Motorcycle Diaries, and that has to do with the fact that I worked on both films with an extraordinary sound engineer, Jean-Claude Brisson. Jean-Claude is very faithful to his Nagra, and I am very faithful to Jean-Claude! So we basically worked in a very simple and direct manner. But of course during the post-production process, we benefited from the remarkable possibilities of digital technology.

"In terms of its concept, the film follows almost the opposite route we had chosen for Central Station, in the sense that the more these two travellers go into the heart of their continent, the more sound they perceive. At the beginning of the film, in Buenos Aires, there are not that many layers in play, but when we reach the Amazon, there is a much richer palette of sounds. The abundance of sound in the Amazon is perhaps the most extraordinary I have ever been exposed to."

But it must have been a temptation to succumb to the exotic, and the film could so easily have become like a travelogue. "Absolutely, but we wanted to be able to integrate whatever sounds we felt could better explain the time of day we were in. The heat is transmitted, as it were, by a constant sound you have in the jungle, a sibilance, as associated with the images of heat, which has a very powerful quality in that part of the world.

"In the Amazon sequences, we used an additional sound engineer, working with a DAT and capturing very specific sounds in the jungle. But we didn’t use those layers in a random form. We used them specifically to help the spectator understand what time of day we were in, and what temperature the characters were actually enduring. Sound can be extremely powerful in this regard, as powerful as music actually."

What percentage of Salles’ dialogue is looped and what percentage recorded by a boom mike? "In the case Central Station or The Motorcycle Diaries, around 90% is direct sound, and 10% may have been looped for technical or performance reasons. As I work a lot with non-actors, direct sound is very important for me. I never loop dialogue with non-actors. You either have it when you’re shooting, or you don’t. Also because of the search for authenticity, you tend to go deep into each locale, in that most of these films are road movies, and so you never go back to re-do things. The voice-over in Motorcycle Diaries is obviously ADR’d. Most of the voiceovers were recorded as we were actually shooting the film, in order to have an idea of the time required."

To everyone’s delight, the song from the closing credits of The Motorcycle Diaries won an Academy Award this year. "That song was actually conceived in one night," recalls the director. "We were working with Gustava Santaollala who composed all the music for Motorcycle Diaries, and who I had met thanks to Alejandro González Iñárritu. Gustavo’s first score was for Amores perros, followed by 21 Grams and The Motorcycle Diaries. Gustavo is the ultimate renaissance man, because he plays most of the instruments you hear in The Motorcycle Diaries. At one point, as we were reaching the end of the edit, we thought to ourselves, ‘Wouldn’t it be great if we had a song for the end of the film?’ So we invited Jorge Drexler, an Uruguayan, a kind of Leonard Cohen of Uruguay. I phoned Drexler, whom I had never met, and we talked about what the film meant, and he knew the book we had based it on. He said, ‘Well, let me think about it.’ The following day at around 10 a.m., he called me and said, ‘Listen to this.’ And he had composed the song through the night and early that morning. He recorded the song in his house, and that recording actually made it into the film. We re-recorded the song, but it didn’t have the quality that the first take had – the one he’d recorded in the comfort of his own house! And it won the Oscar!"

Is sound 50% of the experience in modern cinema, then? "Well, everything is 50% in cinema! An interviewer once asked the great French director, Jean-Pierre Melville, what made a film a good film in percentage terms. And Melville replied, ‘50% is the choice of story you want to tell, and 50% is how you’re going to translate that story into a screenplay, 50% is the sound of the film, 50% the music, 50% the image, and so on and so forth. And if one of these elements goes awry, you’ve just jeopardised 50% of your film!’

"So we are in a medium in which every single element must form part of the whole, and I think that sound is an extremely important part of that equation. The more I make films, the more I believe that sound is a decisive factor in how you decode a film. Can you conceive of Apocalypse Now, for instance, without that extraordinary sound design by Walter Murch? Can you think of the impact of The Conversation without sound – it would be impossible to imagine that as well. Or Altman’s Nashville and A Wedding. So we don’t have to go those very high-end disaster films to establish that sound plays a decisive role in the public’s perception of a film!"

I asked if, when visiting festivals with his films, he sometimes finds that the sound is played too loud, or that the front speaker is swamped by the surround speakers because the projectionist wants to give the audience a real jolt?

"At a festival screening, I normally try to balance the level myself, on the night before the screening when we’re usually allowed to run one reel. So I pay a lot of attention to that, to ensure that the sound is not overbearing, but also that it’s not so dim that it would influence people’s perception of the film. So to find the right balance is extremely important, and sometimes not easy to achieve when you play the film in an empty theatre, because of course the fact that the cinema is crowded will affect the way sound travels within that theatre. What I find more disturbing is how films are projected, for instance, in Brazil, or in other developing countries, where they tend to augment the level of the surround speakers and diminish the front speaker volume. As most presentations in Brazil are of Hollywood films, which use subtitles, people don’t care too much for the dialogue. Or at least that’s what the managers of multiplexes think, when in fact people do care. And even more so when you are showing a film that has no subtitles – a Brazilian film in Brazil, for example – sometimes you find yourself in a situation whereby the film you have mixed so carefully doesn’t sound as it should when it reaches the public because of that manipulation of the surround."

Does he feel able to influence the transfer of sound and image of his films when they reach DVD?

"Well, more and more now, because we normally prepare the DVD track and the 5.1 digital track in the same week as we do the transfer for the release prints. This allows you to be a little more precise than you could be earlier. But for the films I did prior to Central Station (for instance, Foreign Land), the sound transfer is not comparable to what it was when the film was released, and I intend to re-do it, actually."

Does he give some consideration to video screen size when framing? How much is the choice of close-up angle versus wide angle shot dictated by the small screen? "I never think about that at first, but for example when shooting The Motorcycle Diaries, we framed the film in 1:1.85 and we used a matte in order not to allow for a 4/3 re-framing. Of course certain territories will certainly re-frame the film, but at least you can be sure that the microphone is not going to suddenly appear within a shot – as it does occasionally in places where you don’t have 1:1.85 mattes in the projection, and then microphones start to pop up in the upper or lower part of the frame – which is not exactly what you want to see!"

Does he believe that the home experience will ever be the same as it is in a big theatre? "I don’t think so, because as Fellini once said, we go to the movie theatre as we go to a cathedral, that is, to have a collective experience. Trying to see a comedy in the privacy of your home is just not the same as seeing it with four hundred people in the theatre. There is that catharsis that stems from the collective laugh! When your neighbour starts to laugh, you feel relieved as well, and something of a contagious nature occurs. The same is true for any impactful, emotional filmic narrative. In the movie theatre, there is something that travels from one spectator to another that makes that collective experience unique."

He agrees that DVD technology has enhanced the home experience – and the reach of a film beyond its initial theatrical run. "It’s as if the journey of the film can expand beyond the boundaries that existed five or six years ago. I also have high hopes for digital projection,, because in smaller communities outside the big cities, you sometimes don’t have enough of an audience to justify building a theatre, the manufacture of prints etc. – all that is very complicated. But maybe with a digital project, and the digital sound that comes with it, you’ll see a rebirth of the collective experience of cinema in smaller towns throughout the world. If that happens, it will mean a genuine democratisation of the distribution process.

"When an independent film is bought in a country like Brazil or Argentina, there are rarely more than two or three prints, and that represents a significant portion of the final expense for the distributor. With a digital disc, they will be allowed to have more copies, of course, and those copies can be sent to different parts of the territory at the same time, to theatres that may be somewhat smaller than those we have now, but that will attract audiences who are just not going to the cinema at this stage. So I think that the technology will help to build an audience for independent films – at least I certainly hope so!"