Kim Lajoie's blog

That pumping effect

by Kim Lajoie on May 20, 2009

So you’ve probably heard enough of that pumping effect by now. Yes, that pumping effect where the whole mix ducks to the kick. Or at least ducks in time with the music. Or at at least some instruments in the mix. Or something.

If you still think it hasn’t gone out of fashion yet (or maybe you’re waiting for it, like hard pitch quantisation, to come back in fashion) you might be wanting to brush up on your technique. Or you might want to explore some different techniques to come up with something new and different. Or maybe you’re just a sucker for punishment. There are four main ways to approach this:

Straight full-band compression

This is how it was done in the old days – a big kick drum in the mix, and a compressor on the mix bus. For the most distinct effect, the kick should be just loud enough that it should be the highest peaking sound in the mix. You can check this by looking at the peak meter on the mix bus. The kick is loud enough when the peak meter jumps up whenever the kick plays. The mix bus compressor should then be set so the threshold is just low enough that it is triggered by the kick and nothing else. With a high ratio, fast attack and medium release, you should be able to hear the effect pretty clearly. For a stronger effect, use a higher ratio.

Full-band compression with pre- and post-emphasis

For a more dramatic effect than straight full-band compression, insert an EQ on each side of the mix bus compressor. That is, one EQ before the compressor and one after. Set the first EQ to boost the bass significantly (for example, a low shelf +9dB at 150Hz) and set the second EQ to make the opposite cut (for example, a low shelf at -9dB at 150Hz). Coupled together, you should hear an unchanged frequency response. However, what the compressor “hears” is a mix with a LOT more bass than usual. With a strong kick, this can make the compressor behave in an exagurated, slightly unnatural manner. Which might just be what the doctor ordered.

Sidechaining

The two above techniques will fall down, however, on mixes with very strong basslines and relatively weaker kicks. This is expecially so where the bassline is voiced very low and is fairly constant (always sounding, without rests). In these cases, you might want to try true sidechaining. This is where the compressor on the mix bus is operating on the whole mix, but is only “listening” to a separate feed which has the kick drum on its own. Not all compressors can function in this mode, and the ones that do can be fiddly to set up and control.

LFO modulation

Another approach is to use an effect with a tempo-synced LFO. You’d have to set the LFO period to a crotchet (a quarter-note), and its shape to a rising saw. Then assign that LFO to control the gain of the plugin. Volcano from Fabfilter[1] can be configured like this. Apparently Camelphat from Camel Audio is also capable of this, though I haven’t personally tried it myself. The advantage of taking this approach is that being able to adjust the shape and depth of the LFO gives you different, and sometimes more intuitive, control over the sound of the pumping.

While it’s often written that the effect is always produced by side-chained compression, there are other ways of achieving it. Sometimes the obvious solution is not the most appropriate one. And sometimes trying something new can take you places you never thought you’d go…

-Kim.

[1] Disclaimer: I have a professional relationship with Fabfilter.

2 thoughts on “That pumping effect

  1. Alex says:

    Hey Kim,

    Great blog. You have a great knack for explaining things with clarity.

    I find the custom shapes in Sound Toys Tremolator great for the increased control you talk of.

    All the best,

    Alex

  2. Pingback: Five compression mistakes and how to avoid them. « Kim Lajoie’s Blog

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