The basic idea was, 'I heard [Isao] Tomita's music of Holst's The Planets in 4-track'. In the 1970s, there was a brief moment where people installed 4-track sound in their homes where you had two stereo speakers here and then two other speakers in the back of the room. And Francis [Ford Coppola] said, 'That's how I want the film to sound. And Tomita's going to be doing the music.' And as it transpired Tomita wound up not being able to do the music because of a contract that he had with his record label to produce a number of records, he just didn't have the time.

But this idea of the 4-speaker array survived and not only survived but blossomed into a 6-track arrangement. And what I observed at the time was, we can't really do 4-track because unlike music, film has dialogue and the dialogue needs to have its own speaker right in the centre of the screen so that when people speak it's not a phantom centre, but it's a direct projection of sound from centrally behind the screen. So we need five tracks, and Francis said, fine. And then as the meeting was breaking up he said, 'And one other thing, when explosions happen, I want the audience to feel the explosions, not just hear them. So I want the explosions to be like real explosions and have frequencies down below the audible frequency range which is roughly around 25 cycles per second.' Human hearing goes from let's say 20 cycles perhaps to 20,000 cycles and he wanted to go lower than that so your guts and your lungs would vibrate even though you might not hear that sound with your ears; your body would pick it up. And I said, 'Okay, I think that's another track. We need six tracks now.' And that will allow us to fly a helicopter around the theatre because we have speakers all the way around the theatre, and it will allow the dialogue to have a central spine. And we'll also have a channel dedicated to this low frequency because we'll have to have speakers that haven't been built yet, we have to design speakers to go that low.

And that was the beginning of what actually turned out to be what we now call 5.1 sound, which is now the standard soundtrack for films. Now, of course, there's 7.1 and 8.1 and Dolby has a new system called Atmos that is, theoretically anyway 67.2. [sic – it is 62.2] But the basic core of the idea is similar in each case. You want to be able to manipulate sound in an environment in a completely free-form way. Where do you want the sound to come from? Up there. You can do it by manipulating the faders and the joysticks on your control. And you want to have control over the frequencies that go down below human hearing so that the theatre can shake when there's an earthquake or when there's a big explosion or even in the music and in the sound effects so that you have available to you this very wide frequency range.