In which situations is Audio Expansion applied (opposite of compressors)?

Question

I've encountered from time to time some plugins that allows a threshold and a ratio to be set so that quieter sound can have an even more quieter level (or silenced altogether). Ableton Live actually has one in it's multiband compressor which, IMO, is very intuitive to use.

I'm curious as to when would this typically be used though? Is it most often used as an effect? Is it used to do mixing corrections? How about mastering? Is there any cases in Audio Production that this would be my "go to" signal processor of choice?

How is it most commonly used and what benefit does it provide?

Answer 1

You should use an expander when an outright gate will sound really unnatural (and that is not the desire). For example, if your vocalist has a really distracting breathing sound when idle, an expander will reduce that without completely eliminating the attendant ambiance that makes a track sound coherent (which is why it's important to record a minute or "silence" when doing location recording.

I personally try to use it over a gate whenever possible, especially if the recoding was tracked in an ideal or characterful situation. No reason to suck the life out of the "silences" if you don't have to.