Exploding Bridges and Bowling Pins

In Sam Wasson’s fantastic new book about Francis Coppola and American Zoetrope, he quotes Walter Murch ruminating on the sound of colliding bowling pins. I remember those pins well.
When the helicopters attack the village in “Apocalypse Now,” a wooden bridge gets blown up by American rockets. As one of Walter’s assistants, my main job for many months was finding sounds to use in the film. We didn’t have access to any of the big movie studio libraries, and there were pretty close to zero commercial sound libraries in those days, certainly none that had Vietnam War related sounds, so we had to go out and record a high percentage of the sound effects we needed for the film.

We could have found a large wooden structure to blow up

Walter showed me the sequence where the bridge is attacked, a section of it shattered. It looked like several tons of timbers and planks splintered and flying through the air, banging into each other. We had recorded lots of explosions for the movie… grenades, bombs, gasoline, etc., but nothing where big pieces of wood get exploded. We could have found a large wooden structure to blow up, but that would have been expensive, and there was no guarantee that we’d get the wood aspect that we wanted. Very little useful sound was recorded on set while they were shooting the movie. It was way too chaotic, so we had to invent nearly all of the sound in post production. To make the sound of that moment feel authentic, I needed to find woody elements to add to the basic explosion sounds we had already made in post.
I tried lots of things: trees being chopped down and falling, hitting wooden telephone poles with sledge hammers, throwing pieces of lumber around, etc. I think any of those sounds could have been useful layers, and a couple of them were helpful, but they didn’t quite sell the moment. I wracked my brain to come up with situations in which lots of pieces of wood collide with each other. The idea of bowling pins bubbled to the surface.
I suspected it could be a waste of time. Bowling pins are small compared to the size of the structural parts of the bridge in the movie. Bowling pins don’t typically shatter like that bridge wood did. And the sound of bowling pins is so identifiable and familiar… wouldn’t people in the audience recognize that sound immediately, and wonder why they were hearing a bowling alley in a battle scene?
What the heck, I spent about an hour recording in a San Francisco bowling alley. They let me put microphones in various places, including at the back of the alley, behind the pins. When I got the recordings to the studio, they definitely sounded woody, and it was cool that there were a bunch of hits in close time proximity, so I wouldn’t have to build a mass of them individual hit by individual hit. But to my ears they were so obviously bowling pins, and the sound of them felt too small to be elements of so large a bridge.

We didn’t have digital sound processing in those days, but we could make a recording on tape sound bigger by slowing down the tape playback speed, then transferring it at the slower speed. I played the bowling pin recordings at half speed and one quarter speed. Now the pins sounded like they were about ten feet tall. What wound up in the movie was a mix of regular speed, half, and quarter speed pins colliding. As to whether it’s too recognizable as bowling pins… the idea seems never to have occurred to anybody but me. I still hear that bowling alley when I watch the scene, as I did yesterday. To everybody else, it feels like we had microphones all over that bridge. Such is the power of sound design.