Compression and the ADSR Envelope

I’ve got another way for you to think about compressor controls that might help you make better sense of them. Have you ever heard of the ADSR envelope?

The ADSR envelope is something I discuss in some of my on-site mixing workshops, and it’s a way to describe what happens to a sound over time. In this case, we’re looking at the amplitude of a sound as it relates to time.

ADSR stands for Attack, Decay, Sustain, and Release. These are the four basic phases of just about any sound that describe the envelope. Here’s a little sketch I did of these phases within a sound.

Attack is the initial onset of the sound. Decay is the time it takes for the sound to come down to its sustained level. Sustain is the level for most of the sound’s duration. Release is the time it takes for the sound to decay from the sustain level to inaudibility.

The time for each of these phases varies quite a bit depending on the instrument. For example, a tight snare drum hit has very little sustain and release. An acoustic guitar, on the other hand may have a short decay after the initial pluck followed by a bit of sustain and final release. A bowed instrument like a cello may have a long attack and longer sustain depending on how the musician chooses to play.

Now, think about our compressors. What controls do we have that sound similar to the phases of the ADSR envelope? Here, I’ll give you a hint:

If you’ve been having a hard time understanding the Attack and Release controls on your compressor, think about the ADSR envelope the next time you adjust them. Your compressor’s Attack control affects onset of your sound while the Release control affects the final decay/sustain of your sound. Focus on these parts of the sound while you’re making changes. Some compressors will let you make big changes on certain instruments, but the results can also be very subtle so don’t be afraid to swap between extreme settings when you’re trying to figure this out.

Are there things about compression and mixing you find challenging? I’d love to hear about them. Leave me a comment or drop me a note through my website.