This is fantastic: On transom.org, a site devoted to “channeling new work and voices to public radio through the Internet,” the film editor and sound editor Walter Murch is spending several weeks as a sort of philosopher-in-residence. I learned of Murch’s transom.org appearance through a guest post by the former New Yorker writer Lawrence Weschler on one of my favorite sites, Design Observer.

Murch has won Oscars for both film editing (The English Patient) and sound editing (The English Patient and Apocalypse Now)—a remarkable achievement, given some of the very different skills those two jobs require. Murch is responsible for at least one of my all-time favorite film sequences: the scene in The Conversation where the surveillance expert Harry Caul (played by Gene Hackman) assembles a listenable mixdown from several shoddy recordings of a single conversation. The sound editing in that scene is a perfect example of Murch’s genius.

In several essays and a discussion thread in his special transom.org section, Murch relates a number of details about the ways the human brain processes sound. He then explores how these details inform the arsenal of techniques a sound editor must use to impart complex, multilayered audio information without smothering the listener in a gelatinous blob of noise. The extraordinary centerpiece of Murch’s transom.org residency is his detailed breakdown of the various threads of sound that run through the monumental “Ride of the Valkyries” helicopter sequence in Apocalypse Now. Murch demonstrates his concepts with a series of videos of the scene, each one isolating a separate component of the audio track. As Murch explains, he originally set up the sequence’s audio as six separate layers of sound. But he eventually realized that six layers was one too many: “[A]t any one moment (for practical purposes, let’s say that a ‘moment’ is any five-second section of film), five layers is the maximum that can be tolerated by an audience if you also want them to maintain a clear sense of the individual elements that are contributing to the mix.” In the case of the helicopter sequence, he writes,

I found I could build a “sandwich” with five layers to it. If I wanted to add something new, I had to take something else away. For instance, when the boy in the helicopter says “I’m not going, I’m not going!” I chose to remove all the music. On a certain logical level, that is not reasonable, because he is actually in the helicopter that is producing the music, so it should be louder there than anywhere else. But for story reasons we needed to hear his dialogue, of course, and I also wanted to emphasize the chaos outside—the AK47’s and mortar fire that he was resisting going into—and the helicopter sound that represented “safety,” as well as the voices of the other members of his unit. …

Under the circumstances, music was the sacrificial victim. The miraculous thing is that you do not hear it go away—you believe that it is still playing even though, as I mentioned earlier, it should be louder here than anywhere else. And, in fact, as soon as this line of dialogue was over, we brought the music back in and sacrified something else. Every moment in this section is similarly fluid, a kind of shell game where layers are disappearing and reappearing according to the dramatic focus of the moment. It is necessitated by the “five-layer” law, but it is also one of the things that makes the soundtrack exciting to listen to.

In 2002, Knopf published The Conversations: Walter Murch and the Art of Editing Film, a collection of transcribed dialogues between Murch and Michael Ondaatje, the author of The English Patient.