By the time we mixed THX [1138], the rest of the installation had been finished and we were able to mix it in relatively civilised circumstances. We were still mixing the video, which is interesting given the fact that it was 1970-71, black and white, and at the end of mixing the film, we would then project it with a higher quality film image. There was an interesting phenomenon that happened as a result of that, which is that when we projected the finished film, the soundtrack, which had sounded perfectly fine to us when we were looking at this small, low-quality black and white image, the soundtrack was unbelievably dense and intense. But why? It had seemed, when we ran the film with the video, it seemed fine. Why does it now seem wrong? What are we going to do about it? Why, and what are we going to do about it?

The why seemed to be a general principle, which is that if the visual information is small and poorly defined, and black and white and not coloured, so that the amount of information coming from that screen is very, very low, there is more of your brain available to cope with a very complex soundtrack. And so we wanted the experience to be intense, and so as we were mixing it, we would mix intensely, and everything seemed fine because the image was relatively simple. And that left large parts of your brain capable of dealing with the complexity of the sound. That ceased to be functioning when we were looking at a very large, very sharp, in-colour image. And then it just... The soundtrack was too much, because your brain was so busy processing all of the visual information that you didn't have enough left over to cope with the complexity.

So we went back, and for a day or two, we just... we remixed it, simplifying it, and making it less burdensome for the audio parts of your brain. I don't know where that version, that early version is. I don't think it exists anymore. It would be fascinating if it did exist somewhere, to play it and just see now, you know, 45 years later, what that effect really was like. But it's a general principle that there is a handoff between the parts of the brain that deal with picture, and the parts of the picture that deal with sound. They're not the same parts, and it's not almost, but not quite a zero-sum game, which was clear in that particular instance.