The What and Why of Compression
If you have one thing to remember about compression, understand that its main function is to control dynamic range, which is the difference between the loudest and the quietest sounds in a recording.
So what is compression? Well, you can think of it like a tiny engineer, who is constantly riding the faders to adjust the level, so that there’s consistency across an entire recording.
Compression settings determine how active that tiny engineer is while keeping the dynamic range in check.
Compression works by reducing the loudest sounds so that they fit into a smaller dynamic range. The result is that there isn’t as much contrast between the loudest and the quietest sounds. There’s more consistency in the level, and the quieter parts can come through.
If we raised the level of a track so that the quieter parts are heard, it’s possible that the loudest parts might go into distortion, so compression can be helpful in managing the differences.
This is also why compression is associated with making tracks sound louder overall, but it’s actually doing this by reducing or compressing the louder sections to manage the difference between loud and soft.
In mixing, we can use compression to shape individual sounds, so that they blend and balance together. An example would be for vocals. When a vocal has certain words, or phrases that are louder or softer than others, it can be hard to fit them into a mix without some words sticking out and other words getting lost.
In mastering, we can also use compression to shape the tone for various effects. We use words such as “punch” or “glue” or “pumping” to describe these effects. Using compression in mastering, we can also subtly adjust the balance between the rhythm section, melody, and harmony.
It takes practice to decide if you need to compress your audio and how to dial in just the right amount. When mastering, the right amount is related to the way the audience will listen to the audio, combined with consideration of musical style.
Some styles want more dynamic range than others. For example, a podcast that people might enjoy on earbuds while riding the subway or driving in their cars might need more compression to be intelligible in the noisy environments, while an orchestral recording that people will enjoy in the quiet home environment might need little or no compression, so that it maintains all of the impact and energy the dynamics in the music provide.
We might make different judgements for different styles, but the basic concern is the same across all of them — that the listener gets enough dynamic range to feel the impact of the audio, but not so much that they have to adjust their listening level.
In our course, we’ll explore many different aspects of compression. We hope you enjoy them!