Research Guides Home: DSP Audio Effects: Compression/Expansion

Definition

Compression in audio production reduces the dynamic range of a sound by making loud signals quieter and quiet signals louder, helping to create a more balanced and controlled mix. Expansion does the opposite: it increases the dynamic range by making quiet sounds quieter and leaving loud sounds unchanged, often used to reduce background noise or enhance punch.

Dynamics Basics

Dynamic range compression (Wikipedia)
Dynamic range compression (DRC) or simply compression is an audio signal processing operation that reduces the volume of loud sounds or amplifies quiet sounds, thus reducing or compressing an audio signal's dynamic range.
Audio dynamics 101: compressors, limiters, expanders, and gates (iZotope)
Audio dynamics processing is a major part of mixing in music production. In this article, we discuss the basics of dynamics in audio..we’ll demystify the compressor and other audio dynamics processors. We’ll cover the four main types of plug-ins used to control dynamics: limiters, compressors, expanders, and gates.

Expander Basics

Multiband Compression

Compression Basics

Select Compressor & Expander VSTs

Analog Obssession (Free Dynamics VSTs)
Excellent, free, VST dynamics plugins.
MJUCjr
Free variable-mu compressor.
TDR Molotk
Free, VST vintage emulation of multiple Soviet-era audio compressors.
TDR Kotelnikov
High quality, free VST mastering buss compressor.
Best Free Compressor Plugins 2022
This video explores a variety of free compressor plugins, offering a diverse range of options for adding color, character, and control to your audio. From vintage-inspired emulations to modern digital compressors, the video provides a comprehensive overview of each plugin's features and capabilities, allowing you to choose the best fit for your needs.
OTT Aggressive Updwards/Downwards Compressor
Xfer Records OTT is a free re-creation of a popular aggressive multiband upwards/downwards compressor set-up used by many dubstep and electro producers.

Upwards Compression

Compressor How To

How to Use a Compressor (Easy Beginner’s Guide)
Learning how to use a compressor is one of the most important mixing skills you can acquire. Compression is quite literally all over mixes, even becoming the sound we associate with loud, modern pop mixing. If there’s anything you want to really understand, it’s compression and how to use it effectively.