What Is Sidechain Compression?

Before we talk about the sidechain, it’s important to talk about compression. Compression is used heavily throughout the Dreaming City album. Taking inspiration from electronic music group Justice, compression is the glue of the album.

Limiting Compressors

Songs throughout the Dreaming City contain many samples, ambient noises and trippy reverberations. These sounds aren’t necessarily cohesive when played together, but when pushed through the same compressors, the sounds begin to mesh. Two pieces of music or sound may mesh when their notes are in the same key, but also when their effected by processing in the same way.

With a Limiting Compressor, sound begins compressing if the volume reaches a certain level, called the “Ceiling”. Everything past that level is heavily compressed, and is said to be “Limited”. The goal is to compress the sound so it’s not to go louder than the ceiling.

Compressor controller showing the compressor Ceiling set to -0.1dB and a Threshold of -9.7dB. True Peak limiting is enabled.
The limiting compressor used in the song Length of a Moment (Feat. Steven Clapham)

The other parameter is the “Threshold”, which enables gain compensation to boost sound that is quieter than the specified level. This shifts all sounds into a loudness zone, where nothing goes quieter than the threshold and nothing louder than the ceiling.

Sidechain Compression in the Dreaming City

Overall, sounds are all filtered through the master limiting compressor, but individual elements are first affected by their own compression. In this album, all bass heavy synths have sidechain compression applied, to let the drums push through the mix.

Sidechain compression takes one sound as an input and one sound as the effector. The input sound decides how much compression will be applied to the affected sound. In my mix, the input is almost always the kick drum. When the kick drum hits, the compression starts, and the affected bass synth is dampened, allowing the kick to sound large and full of bass.

Sidechain compression in Length of a Moment (Feat. Steven Clapham)

In the preview above, the top module is listening to the kick drum, displaying it’s volume over time. Below is the compressor, affecting the bass synth. On the right side of the compressor, you can see the gain knob ducking in sync with the kick hitting. Listening to the bass, you can hear how the sound seems to pulse with the kick, when usually the bass line would sound like a constant tone.

This form of compression applied to the bass synth is constant across it’s audio level, unlike most compression. This means no matter how loud the bass is, it’s signal will be lowered by the kick drum. If the bass was more dynamic, and included quieter elements, along with louder elements, that worked with the kick, then a more typical compression would be used. to keep the dynamics of a softer sound, but dampen the louder sounds, the side chain would effect the threshold knob instead of the gain knob. Additionally, the ratio would need to be set to something like 10:1 so the sound within the threshold would be 10 times quieter.

What is Paulstretch?

Paulstretch is a program for stretching audio by extreme amounts, to make a 3 minute song 1 hour long (or more or less).

Sample of Paulstretch

In the above example, I recorded myself saying “Hello” and you hear it played back 3 times with different stretch factors. The first hello is the original sample, a 1x stretch factor. The second hello is 2x and the third is 50x.

Paul's Extreme Sound Stretch Interface. Looks like it's from the 1990's.
Paul’s Extreme Sound Stretch Interface

Using this stretching technique, musical notes can be held for an extremely long time, without producing unpleasant audio glitches. That said, when stretching music, results range from beautiful to creepy and even painful. For instance, stretching an electronic song with a big bass heavy drop, can yield some interesting results.

Flume Stretched

In the above example, the song “Say It feat. Tove Lo” by Flume, is stretched 60x at the start of the first chorus. The first thing I notice is the vocals, with a lot of high pitched static. The vocals are singing “say it” while a clap sample is layered with the start of a big synth chord, but the stretching completely changes the recognizability of these elements. With this technique, unique and evolving ambient synth sounds become quite easy to create.

Using Paulstretch in The Dreaming City

The last few Hous3 albums include samples generated with paulstretch and The Dreaming City was no exception. The easiest to hear an example is in the song “Play Me”, as the whole song was created around this technique.

Hous3 – “Play Me”

The background “synth” that plays throughout the track is all Paulstretched audio. Layers of reversed instruments and string section enhances the sound to not be too much of a blur. When parts of the song are stretched with vocal samples, the moving dynamics of the final sample feels full of depth and complexity, when in fact it is a simple stretching of a short soundbite.

Get stretching

Thanks for reading. If you want to hear more Paulstretched music, check out the song “Future Night Club” on Spotify. Or see if you can spot some less noticeable samples throughout The Dreaming City album. And if you have any music featuring Paulstretch, please let me know!