Anatomy of a soundtrack

Dolby consultant Chris Sturmer explores the facets of a typical film soundtrack

King Kong

A long time ago, in a galaxy far, far away, when I was just ten years old, a movie came along that shaped my future.

It was Who Framed Roger Rabbit, and for the first time ever, like everyone else in that cinema, I was mesmerised by cartoon characters interacting with humans on film.

But unlike most of the audience, it wasn't the amazing visual experience that inspired me, it was the sound. Cartoon 'boings' and comedy 'splats' were seamlessly mixed together with everyday noises and magical music. I was hooked, and from that moment on destined to work in the film business.

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In those faraway days (well, 1988), sound was recorded on huge 35mm magnetic tape machines that used noise reduction to suppress the tape hiss. Twenty years later, I'm a film sound consultant for Dolby in a rapidly-evolving industry where movie directors can now carry around their entire film's soundtrack on a single, pocket-sized hard drive. But, even though technology has progressed and film sound keeps achieving new heights, the basics of the soundtrack live on...

The holy trinity

A movie's sound is always split into at least three parts; dialogue, music, and effects. For larger budget films there may also be Foley (human-made sounds such as footsteps and door slams), and atmospheres. A different team is responsible for each of these aspects, and there is a re-recording mixer whose job it is to bring the whole film's sound together.

As for the dialogue, it isn't as simple as it, er, sounds. A sync track will have been recorded at the time of shooting the scene. This could consist of a boom mic and a close mic recording, and may well be contaminated with external sounds such as camera noise, wind machine noise, and rain. So scenes which are deemed to have dialogue recordings that are not up to scratch are then 'looped' and an ADR (Automated Dialogue Replacement) track recorded.

The actors are called into a studio and the scene is looped on a screen while they recreate their vocal performances. These new tracks are then seamlessly mixed into the final version so that no one is any the wiser – unless you know what to listen for. In my experience around 99 per cent of English and American films employ ADR (it's a fairly cheap process).

Take 2

ADR is also used when a director wishes to re-script or add a line and can't go back to re-shoot the scene. For a great example of this have a look at Vantage Point, recently released on DVD and Blu-ray.

During the scene under the bridge at about 1 hour 12 minutes, Enrique's lines, 'What brother?' and 'It looks like we've both been set up,' were added during editing to completely change the context and motivation of the character. Around 30-40 per cent of Vantage Point is ADR, with the re-recording mixer (Jamie Roden) doing an excellent job of controlling the dialogues on such a busy and complicated mix.

Effects tracks open up another facet of the mix – sound design. Sound designers are a very talented breed who create sounds by manipulating other audio elements. Can we record King Kong roaring? Of course not. Well, we'll have to create it then. By running a stock noise of a lion roar backwards, at a slow speed, at a lower octave and layering multiple versions on top of each other, sound designer Murray Spivack was able to create the ape's growl for the 1933 classic movie.

The heat is on

Foley is an area of sound that sometimes gets overlooked, because if it's done well it blends into the scene perfectly. When watching any film, chances are that very few of the footsteps, clothing sounds, or punches were actually recorded live.