Understanding compression

When mixing, we call the range in volume from loud to quiet the dynamic range. Compression is an effect to be applied to a sound to reduce the dynamic range. After compression is applied to a sound, the loudest parts of the sound become quieter relative to the quieter parts. The volume of the whole sound is then raised. Reducing the dynamic range means that you have less change between the quietest and the loudest parts of your sound.

Why would you want to use compression? Imagine you were having a conversation with someone and wanted someone else to hear a recording of the dialog. In the recording, some parts of the dialog might be really loud while others might be quiet. You might whisper in some parts and yell in others; you might move close to or further away from the microphone. All of these factors will affect the volume of the end result of the recording. For someone listening to the recording, you don’t want them to be struggling to hear the whispering and then having their ears blasted off in the louder parts. You want to have a consistent volume throughout to ensure an easy listening experience.

Applying compression to a sound helps to remove these problems. By applying compression, the volume of the loud parts of your audio will be brought down so that they don’t overpower your listener. After compressing, we can bring up the volume of the whole sound, including the quiet parts. The volume of the whispering parts will be increased to a level that is comfortable to hear. The overall result is a recording that’s easy to listen to, with the loud peaking parts tamed and the quiet parts made more audible.

Any sound with extreme peaks in the dynamic range may benefit from compression. After applying compression, sounds generally appear thicker and fuller, which is desirable. The trade-off is that you won’t have as much contrast between sounds.

Let’s see what compression looks like visually. The following figure shows the waveform of a kick drum audio sample before it is compressed:

Figure 6.1 – Uncompressed kick sample

The following figure shows the waveform of the same sample after it has been compressed:

Figure 6.2 – Compressed kick sample

The amplitude (height) of the waveform indicates the loudness. In Figure 6.1, you can see that the dynamic range is large. It’s loud in the beginning but tapers off over time until it becomes nonexistent.

In Figure 6.2, you can see the dynamic range is smaller. It’s loud in the beginning and the volume stays high for the duration of the sound. The volume of the loud part at the beginning has decreased and the quiet tail end of the sound has increased.

When we compress, we bring the loud and quiet parts closer together so that there’s less variation between the highs and lows (less dynamic range), and then usually increase the overall volume of the sound.

Applying compression with Fruity Limiter

Let’s learn how to apply compression to a sound. To illustrate the examples in this chapter, we will use Fruity Limiter, a plugin that comes with FL Studio. Fruity Limiter has multiple tools, including compression, gating, sidechaining, and limiting. We will explore these topics in detail in the upcoming pages. Understanding how to use these tools will give you generally applicable skills used in many synthesizer plugins and effects.

Let’s get started with applying compression with Fruity Limiter:

1. Drag any audio recording sample into the playlist and route the audio to a mixer channel. In my example, I’m using a single kick sound sample found in the Pack folder in the browser. If you need a refresher on routing audio to mixer channels, see Chapter 4, Routing to the Mixer and Applying Automation.
2. In the mixer channel that you routed your sample to, insert the Fruity Limiter effect plugin, and select the COMP setting (which stands for compression), as shown in the following screenshot:

Figure 6.3 – Fruity Limiter

Fruity Limiter is made up of several components: the LOUDNESS section, the ENVELOPE section, and the NOISE GATE section.

The LOUDNESS section is a compressor. The following are descriptions of the controls from left to right:

• GAIN: Increases or decreases the overall volume. After applying compression to the sound, the louder parts will be quieter. This means the loud and quiet parts of the sound are closer together in amplitude. You can then increase the volume of the sound as a whole by increasing the gain.
• SAT (saturation): This is a form of mild distortion. It affects the louder parts (higher amplitude) of the sound more than the quieter parts. In electrical hardware, this occurs by overloading the electrical component. The more signal you apply, the more the sound gets saturated. If you combine saturation with compression, the compression brings down the volume of the louder parts. This results in the quieter parts of the sound being closer in amplitude to the louder parts and allows more of the sound to receive saturation.
• THRES (threshold): This sets the level above which the signal will be compressed. If the threshold is set to 0 dB, it disables the threshold and no compression will be applied.
• KNEE: This determines the transition between no compression and full compression. It allows you to fade in the amount of compression.
• RATIO: This determines how much compression should be applied once the threshold is exceeded.

By adjusting the threshold, knee, and ratio controls, you can compress the sound of the audio. The following screenshot shows an example of applying compression:

Figure 6.4 – Threshold

To apply compression similar to the preceding screenshot, do the following:

1. Have the sample playing while applying the compression.
2. Set the THRES control level to a value below 1.0. This determines what volume to start applying compression at. Anything above the threshold level will have compression applied to it. You can set the KNEE control if you want the compression to fade in instead of coming in abruptly. The lower the value you set the threshold to, the more you will notice the sound of the compression.
3. Set the RATIO level to a value greater than 1.0:1. This will determine how much the sound is compressed. If the ratio is set to 2.0:1, this means that for every dB in volume, the signal will be reduced to half. If the ratio were 3.0:1, then the signal would be reduced by a third, and so on.
4. Increase the GAIN level of the sound. After adjusting the threshold and ratio controls, the volume of the sound has decreased. The loud parts of the sound have been lowered to a level closer to the volume of the quieter parts. We now apply what is called the makeup gain. This will increase the overall volume and result in an ending sound where the quieter and louder parts are brought closer together. This makes the sound appear fuller with less dynamic variation.

Congratulations, you just applied compression to your sound!

Let’s continue exploring the Fruity Limiter plugin. To the right of the LOUDNESS section, you can see the ENVELOPE section, as shown in the following screenshot:

Figure 6.5 – Envelope

Transients are the short burst of energy that you hear at the start of any sound. The envelope provides control over the ATT (attack), REL (release), and SUSTAIN levels of the transients.

The ENVELOPE section here is applied to the compression. You won’t hear any difference when you use these controls unless you compress the sound first.

By decreasing the attack of the compression, you cause the compression to come in quicker. This will reduce the punchy articulation of the sound.

By decreasing the release time, the sound becomes shorter and brings focus to the loud, punchy peaks of the sound. This is because decreasing the compressor release means that the quieter part of the sample isn’t amplified for as long. The opposite is also true – by increasing the release time, the sound becomes longer, and you can hear more of the compressed tail after the makeup gain.

The SUSTAIN control allows the compression to last longer or shorter.

In the bottom-right corner of Fruity Limiter, you can see two circle icons with arrows, called store in spare state. These buttons allow you to flip between two states of the plugin to give you a before-and-after comparison. Essentially, you get two alternative setups that you can switch between and compare.

Fruity Limiter contains several presets in the top-right corner of the plugin. I encourage you to experiment with the presets to see examples of compression.

Understanding parallel compression

If you look up the term compression online, you may come across the term parallel compression. Parallel compression is where you have two identical sounds being played simultaneously. One of the sounds has compression applied to it, while the other doesn’t. You have a compressed sound and an uncompressed sound.

The benefit is that you get the emphasized part of the compressed sound without losing the original transients. When you compress a sound, you make a trade-off. You lose the impactful loudness peaks of the original sound and trade it for a thicker, fuller-bodied sound that emphasizes more of the quieter parts. The hope is that the fuller-bodied compressed sound is more pleasing to the ears.

In parallel compression, you don’t have to make this trade-off. You layer the uncompressed version with the transients with the compressed sound that doesn’t contain the transients. You gain all of the benefits of compression while leaving the delicate transients intact. The result is a thicker, fuller sound that still maintains the punchy articulations. Parallel compression is most often used on drum instruments to maintain transient punchiness.

So far, we’ve covered simple compression and parallel compression. Let’s look at another type of compression, called a gate.