One of the most common music-related questions I get is, “What is Compression?”

Here, I hope to answer this for any of my customers, new employees, or anyone who is curious.

Many words have more than one meaning and “compression” is one of them. When it comes to music, there are two main types: data compression and dynamic range compression.

Data Compression

MP3 is the most common example of this type. When you need to store files like music, photos, or videos, and need to save space, you can shrink their size by compressing them. Different methods exist, each with their own pros and cons, depending on what you are working with and trying to do. WMA is better for music than MP3, but is not as widely supported by playback devices. Both are “lossy” methods of compression, meaning that you lose quality in the process in exchange for the small file sizes. If you have plenty of storage space, you can use WMA Lossless, FLAC, or other methods that – in theory – still save you space, without any loss of audio quality.

Dynamic Range Compression

This one is strange, because it is used for the exact opposite of what it does. If you ever hear a producer mention “compression” without specifying which type, this is probably what they mean. Dynamic range in music is the difference between the lowest and highest volume of what you are listening to and compressors bring those two things closer together by keeping volume from going up too much once it reaches a certain level. I like to think of it as a seat belt or rubber band that keeps sound in check.

But here’s the thing: hardly anyone realizes that compression makes sound quieter, not louder. The reason is that, after a signal is compressed, its level is usually raised in order to make the track sound as loud as possible without distorting. So in the end, the loud parts stay where they are and the quiet parts get raised.