Ambient Sound That Never Repeats: How Generative Audio Works

The trouble with a loop

Open most ambient sound apps and you're hearing a clip, somewhere between ten seconds and a few minutes long, playing again and again. That is simple and reliable, and often it's good enough.

But once you have learned a loop, part of you starts waiting for the bits you know. The wave that always crashes at the same moment. The bird that calls on schedule. I wrote about this in why lo-fi stops working and why recorded rain eventually doesn't work.

What "generative" means

Brian Eno made the word popular. Wikipedia gives his description: music that is "ever-different and changing, and that is created by a system".

So nothing is stored and played back. A set of rules runs, and sound comes out for as long as it runs. It is closer to an instrument that plays itself than to a music player.

The idea is older than computers. There is a short version of that story in a short history of generative ambient music.

How mine works

I used a picture where a composer would use a score. Shapes drift slowly across the screen, each at its own speed. The kind of shape decides the kind of sound.

Nothing plays by itself. Sound happens when two shapes overlap, and you can drag them together yourself. More in shapes as instruments and sound only happens when things touch.

None of it is recorded. Every sound is built on the spot in your browser, which is why there are no audio files to download.

Why it stays calm

Chance alone gives you noise. What keeps it pleasant are the parts that are fixed.

• One scale for everything. All the sounds in a world share the same set of notes, so any two that meet will fit.
• A limit on how many sounds play at once. When a lot of shapes cross together, the scene doesn't turn into a wall. See voice limits.
• Soft starts and slow fades. Nothing jabs at you.

Getting that balance right took far longer than building the shapes themselves.

What "never repeats" does not mean

It means there is no loop point. There is no stored sequence, so there is nothing to come back round to.

It does not mean endless novelty. The set of sounds is fixed. After a while you will know the whale call and the sonar ping. What keeps changing is when they arrive and what they arrive next to.

Three worlds

Ocean is free. Forest and Space are unlocked together by a one-time payment. All three run on the same engine with different sounds, scales and rules, which I describe in three worlds, three sets of rules.

Sources

• Generative music, Wikipedia