I came across a video on my social media feed that shows how they created the sound effects for an animated film at Walt Disney in the 1940s and was struck by the ingenuity used to create the sounds, and wondered if these techniques can still teach us something today.

In essence, the limits of the technology available at the time forced the Disney team to be very creative to find ways to produce credible sounds.

The challenge was they needed to bring the sounds they needed into the studio as mobile sound recording was still in its infancy and wasn’t really suitable for any more than recording dialogue.

In 1935, Walt Disney hired Jimmy MacDonald, and he began designing and creating things like wind and rain machines, glass jug motors and bow frog ribbits which bizarrely could be used to recreate the natural sounds out in the world.

To create the sounds in the studio, two different techniques were developed.

• One was to use musicians to create some sound effects using both conventional musical instruments and percussive instruments like timpani, bells, cymbals and blocks.

• The other approach which really stood out to me when I watched this video was the elaborate sound effects machines they designed and built to replicate the various exterior sounds.

In both cases, ‘musicians’ and sound effects people used all these tools to create the required sounds in sync with the film being projected onto a screen for the performers to be able to see and play live to create all the sounds needed.

Let’s take a look…

Now you have seen it, I am going to take you through the film scene by scene and share my observations…

The film starts with the train’s bell. Notice the intense concentration of the person ringing the bell to make sure they could the bell absolutely in sync with the animation. No scrubbing it up and down the timeline to get it exactly in sync. Note that there are no other background sounds just the sound of the bell. It’s only at the next cut that the sound of the steam engine is introduced.

As the train starts off, most of the steam puffing sound is produced by what appears to be a very complicated machine where the operator turns a valve, which produces each puff, whilst another valve allows a small amount of ‘steam’ to be released to create the continuous hiss. Also, notice the cellist playing in sync with the steam operator, adding another layer to the sound of the train, all in one pass.

To get the sound of the wheels on the rails, instead of a linear track, they have designed and built a circular track, which the operator pulls round and round.

Then to add another layer, they have taken what looks like a lawn mower cutter head and used that as the basis of a machine that creates a constantly rotating and clanking sound, which is added in on the fly.

For the next scene, two musicians play some kind of wind instrument to create the cows mooing. Again look at their faces as they concentrate on the screen to help get the sounds perfectly in sync.

As the train crosses the bridge the puffs of steam and smoke lift the tiles on the bridge roof and play a tune. The tune is created from a series of tuned jugs, each of which produces a note as the lid is flipped up and closed. Again all played in sync as the film is projected onto a screen in the studio.

Once the train emerges from the bridge, it realises that the next bridge is no longer there and, through its steam whistle voice, calls out, “bridge out, help!” This seems to have been created by an actress using a throat mic which was presumably then fed through what must have been a very early vocoder. So I did some research and learned it could have been a vocoder as it was invented in 1938, just three years prior to this film, and we know that Disney used vocoders.

It was invented by Homer Dudley at Bell Labs as a means of synthesizing human speech. This work was developed into the channel vocoder, which was used as a voice codec for speech coding to conserve bandwidth in transmission in telecommunications.

By encrypting the control signals, voice transmission could be secured against interception. Its primary use in this fashion is for secure radio communication, and it was used to scramble transatlantic conversations between Churchill and Roosevelt during the second world war. The advantage of this method of encryption is that none of the original signal is sent, only envelopes of the bandpass filters. The receiving unit needs to be set up in the same filter configuration to re-synthesize a version of the original signal spectrum.

How A Vocoder Works

A vocoder blends two sources, usually a human voice - the Modulator, which is broken down into several bands using series filters. The Carrier is the synthesizer component of the vocoder, which substitutes a traditional oscillator stage by using a frequency analysis of the Modulator as an audio trigger.

In less technical terms, singing into a microphone and playing keys on the vocoder will trigger the pitches played, producing a multi-voiced, harmonised, and otherworldly performance interpretation of the words and notes you sing.

However, further research shows that it might not have been a vocoder. It could have been a Sonivox, a device described as looking like two tin cans, which were held to either side of the performer’s throat. Apparently, although the audio from the Sonivox had a metallic quality, it had the advantage of keeping the actor’s performance.

I have not been able to establish whether it was a Vocoder or a Sonivox used on this particular film, but either way, it is clear that Disney was up for investing in new and innovative tech and had both devices around this time, and we do know that it was the Sonivox that Disney used for Dumbo in 1941.

At the same time, as calling out, “bridge out, help”, the engine brakes hard, and the sound for this is a piece of metal scraped across a pane of glass. Simple, but very effective. You can even see the scratches across the glass from previous uses.

As the train falls into the abyss, the score takes over and gives the cues of falling.

Finally, the sound of the train crashing into the ground is a carefully set pile of objects that, on cue, the operator pulls out a carefully placed prop, and the pile comes tumbling down.

And there you have it.

What Can We Learn?

The techniques may differ from what we use today, but the planning and prop time would have been significant, as they are today. The machines that Disney’s team had to design and create would have taken some serious development time. But once perfected, could be brought out again and again. So instead of a library of sound effects on tape, CD or nowadays on hard drives, they had a catalogue of machines and instruments to draw on to build up the soundscape,

What struck me the most was the adage of getting the sound correct, before it hit the microphone. Rather than trying to ‘fix-it-in-the-mix’, their ethos was to create the soundscape and capture it with one or two microphones using human skill to play all the elements together in one pass perfectly in sync with the pictures.

Just because the technology was limited, they were not limited by their creativity. In fact, they had to be even more creative to produce a credible and believable soundtrack using as few passes as possible using the technology at their disposal.

Watching this film, I felt this was the post-production equivalent of the creative buzz that musicians get when they recorded a demo on the likes of a portastudio.

Planned, rehearsed and executed in a single pass. There is nothing to touch that feeling.