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Parallel Compression

I get email from producers around the world every day with questions about ‘how to’ or ‘when should I,’ fill-in-the-blank. A couple of weeks ago, one of those emails inspired a blog post about compression. Today I got a great follow-up question from Mario about PARALLEL compression. In my reply I told him that he was the first ever to ask me about parallel compression and decided immediately that I needed to blog about it today. It’s a valuable tool to have in your arsenal, especially if you get production materials from diverse sources.

About now, some of you are wondering what the hell parallel compression is and why you hadn’t heard of it before. The reason is, it’s something most often used by music producers. It’s one of those magical things they know about, but because radio was late coming to the big multi-track party several years ago, us radio peeps never got that far into the conversation. Parallel Compression is a really nifty trick to add loudness to a track without making is sound like it’s been compressed…it just sounds like it was recorded with more gain in the first place. However, it’s kinda tricky.

Parallel compression is set up pretty much the way reverb is configured and really only works well with a handful of compressors. The original signal is split, using the SEND bus, rather than a regular INSERT on a channel. Compression is applied to the new bus, but NOT the original channel. (There are alternative ways to do this, but this is the simplest.) The advantage is you have instant access to a WETNESS factor or…how much of the signal is compressed and how much is allowed to come through in its raw state. You can drag the bus RETURN fader up and down any time while leaving the original track at parity (±0.0db). The higher the gain is on the return, the higher the wetness of the effect. A good starting point is always 50%. I tend to go down from that, but not always.

Usually, the threshold on the compressor is set rather low so that practically everything is compressed. The ratio is also high, say 20:1, the knee should be soft and the attack is set to slow and release set to a bare minimum. This sets up a kind of ‘umbrella’ you can put over the original to boost the main parts of the track, but allow the original track to handle the beginning and end of individual sounds, giving an overall feeling of a non-compressed signal. Once set up, you might find it best to play with the knee first, if you’re not getting the impact you like.

Proponents say it can add a ‘loudness’ factor without compromising the overall quality of the original track. That claim can be questionable because the quality of the compressed signal must be absolutely pristine. Most compressors just aren’t that good with really high settings like I’ve described.

Music producers most often use it on individual instrument tracks that tend to be much more quiet than others. Thus, you might see it on a bell tree track, but not on the tympani. Of course, it can be used for effect too, so nothing is absolute. (Is it ever?)

Using it on VO has its own set of issues, mainly that when you amplify

a whisper, you not only bring up the VO, you also tend to bring up all the mouth noise, clicks and glottal junk, room noise, echo and hum that

are easier to ignore or otherwise take care of with good noise reduction and EQ. Remember that compression of any kind means less dynamic range, which is really easy to overdo. Like a really good pepper sauce, too much can burn out the taste buds and leave you craving relief. Just the right amount can add a delightful sting that will leave your audience wanting more.

I hope this idea will get you to experiment a little. I find that experimentation leads to all kinds of exciting discoveries and usually makes a producer’s work stand out from the pack.

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