This is just a quick note that I thought would be useful.  I spent about an hour on the phone with a friend of mine who is going through the mind-bending task of mastering his own work.

Question: I’m trying to bring the level up on my mix,  but every time I get to a big level I hear this weird pumping on the track.  What’s up?

One major problem people encounter when using heavy doses of compression on a full stereo mix is the pumping that sometimes occurs.  What this often is, is the loudest part of your mix (usually something transient like snare or kick drum) triggering a slow compressor.  The transient slips by the attack un-compressed, but not before triggering the attack-hold-release pattern of the compressor.

The Result: The audio just after the transient gets attentuated so you hear LOUD KICK followed by everything else pulled way down for just a moment.

A couple of things to try in order to get around this particular kind of pumping (there are others) are all based around turning the loud trasients down before the compressor.

Sometimes simply creating a gentle dip on an EQ before the compressor and corresponding bump on an EQ after the compressor will do the trick.

Failing that, you can try multiband compressors which let you set independent attacks/releases for different frequency ranges – thus preventing a loud bass-heavy transient like a kick from triggering compression on your cymbals and vocals.

The last method I’d suggest would be going back to the mix.  This isn’t always an option due to schedules or budgets, but sometimes simply mixing the transients that are causing pumping a little lower in the mix (sometimes 1dB changes make a world of difference).

Sorry if this isn’t as comprehensive as you might like, but learning how to hear/manipulate compression is a skill that takes time to develop.  Meaning – I’m still learning about the finer points of compression too – so if I’m wrong, stupid, or incomplete, please leave a comment or send an email.  Your flames are greatly appreciated.