We were using this new sound format when we were mixing Apocalypse Now and we were mixing in a theatre designed specifically to mix this way. It was a specially-built mixing theatre in San Francisco that Francis [Ford Coppola] and the film had put together. None of us working on the film had ever mixed even a stereo film, even a normal... Everything we'd worked on prior to that had been mono. It's the old-fashioned soundtracks.

The last film I had worked on prior to Apocalypse Now was Julia, directed by Fred Zinnemann, and it was exactly of a piece with all the film history up to that point, whereas Apocalypse Now was this big break. We were using a computerized board for the first time in film history and we were mixing in this environment. And we had to learn the rules of this. What... Were there rules, and what were they? What could we do and what could we not do?

I approached this situation nervously because I'd never done this before. Nonetheless I thought, given what we have to do, and given the work involved, and given what I know about audiences and how they react to sound, it would be counterproductive for us to mix this film with all of these channels working all the time. Because the ear gets used to an environment fairly quickly and once you get used to an environment, then all of the work that you use to maintain that environment is kind of counterproductive because... In the sense that riding a tiger is counterproductive. You have to stay on the back of the tiger.

So I thought, let's jump off the back of the tiger at fairly regular intervals. What that meant was: there are going to be many places in this film where it is just mono. We have all of these speakers but we're not going to use them. And it's just the narration, it's just ordinary mono sound effects and even the music is just going to be coming out of the centre speaker because that will get the audience used to that sonic environment.

And then, at the right dramatic moment, we can expand to stereo and because it's a new environment, the audience will feel like, aahh, things are opening up. And then at the right moment we can expand even further to the entire theatre and then at the right moment we can go down into lower depths of the sub-sonic realm and then have the film do everything that it can do. And then at the right moment, we shrink back to mono again.