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Learn Music and Audio Production | iZotope Tips and Tutorials

6 Parallel Compression Mistakes in Mixing

by Arthur Kody, iZotope Contributor March 14, 2022
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Using parallel compression can help you enhance the punch and power of a signal without altering the original transients or eating up lots of mix headroom. But, in pursuit of parallel compression perfection, there are some common obstacles that might prevent you from getting the sound you want.

In this article, learn about six common mistakes people make when using parallel compression along with some tips to sidestep them.

Many of these tips include iZotope’s Neutron mixing plug-in. Neutron comes included in Music Production Suite with RX, Ozone, and even more mixing and mastering plug-ins. Start your free trial of Neutron and add parallel compression to your mixes easily and efficiently.

This article references a previous version of Neutron. Learn about Neutron 4 and its powerful features including Assistant View, Target Library, Unmask, and more by clicking here.

Let’s define exactly what parallel compression is and when you should use parallel compression in your mixes.

What is parallel compression?

Parallel compression is the process of blending a compressed music track or submix with an uncompressed copy of the track. This particular type of parallel processing allows you to retain much of the original dynamics of your audio while still letting you harness all the benefits of using a compressor. Rather than adding compression to the entire signal (which can end up really squashing your transients), parallel compression gives you more control over the balance between dynamic and compressed. This is also referred to as New York Compression. Talk about getting the best of both worlds!

Here’s what parallel compression sounds like on an EDM track:

There are many different approaches to setting up parallel compression in your mix sessions. One method involves duplicating the original signal and only adding compression to the duplicate. With this type of setup, you can now blend the two resulting signals together to dial in the right blend of dynamic/compressed. The other is creating an aux buss with a compressor as an insert. You then route the dry signal to the input of the aux track. The aux track will output only the wet signal. You can then blend the wet and dry signals to taste.

Another method for setting up parallel compression is to use mixing plug-ins that allow you to control how much of the original signal is being sent through them. Plug-ins like Neutron offer Mix sliders that allow you to choose how much of the original signal will get processed by the plug-in’s modules. This allows for all sorts of creative parallel processing, but is especially useful for applying parallel compression quickly (and without cluttering your mix session with a ton of extra buses and complicated routing).

Neutron’s Mix sliders are perfect for applying parallel compression
Neutron’s Mix sliders are perfect for applying parallel compression

When to use parallel compression

Because parallel compression can help shape transients while still maintaining a consistent output level, this technique is most often used for helping “glue” drum kits together. But, one way I find myself using parallel compression quite a bit is to help with mixing vocals. If you need to bring more presence to a vocal, but also want to keep the original dynamics of the performance, parallel compression is definitely the way to go.

For compressing vocals in parallel, I like to use the Compressor module in Nectar (iZotope’s dedicated vocal mixing plugin). Just like the modules in Neutron, Nectar also has Mix sliders so you can hone in on the right balance of processed/unprocessed signals. It makes adding parallel compression to vocals a breeze. 

Use parallel compression in Nectar for mixing vocals
Use parallel compression in Nectar for mixing vocals

Although most commonly used on drums and vocals, parallel compression can be used whenever you need to increase the presence and punch of an instrument, but still want to keep the dynamic quality of the original audio. And, you don’t just have to use parallel compression on individual instruments—you can also apply this process to submixes or even your master channel!

Now that you know what it is, how it works, and when to use parallel compression in your mixes, let’s dive into the six mistakes people often make when using this technique.

1. Not knowing what you’re trying to accomplish

As with all mixing scenarios, it’s a lot easier to evaluate your decisions if you know what you want to accomplish in the first place. Compression on its own is a confusing topic, especially for newcomers. And going parallel just for the sake of it can complicate things even further since we’re now using the processor in an excessive way. So, it helps to know why you want to use parallel compression in the first place.

I typically employ parallel compression when working with signals that have clear transients, but quiet, low-level information that seems to get lost among other instruments. If I use compression “normally” as an insert effect, I’ll be able to make the soft hits more noticeable, but I’ll end up having to reduce transient peaks to do so.

By using parallel compression, I get to retain the original dynamics, while adding the necessary attitude that makes the whole thing seem more up-front. Since the compressed signal is mixed at a lower level, I don’t overwhelm the mix with gain either. In this way, parallel compression allows me to apply extreme compression without any of the typical drawbacks.

2. Not compressing hard enough

In a typical parallel setup, the compression should be much heavier than what you would normally use as an insert effect on a track. Because you have the option of blending as much of the compressed signal into your mix as you want, go ahead and really work that compressor to make sure it’s doing its job.

To get that in-your-face bite, try starting with a fairly conservative ratio (with a high level of gain reduction, even low ratios sound dramatic) and pull the attack time toward the faster end of the dial, landing somewhere between 0–5 ms. Since the original signal already contains most of the impact you want, this attack setting tells the compressor to clamp down near-immediately to squash transients, avoiding an overly punchy mix. Additionally, if you’re working with short samples, a long attack won’t grab the signal in time.

Like a usual compressor, attack and release controls are set to suit the material and will change from project to project. You might want more transient energy from the compressed signal, and in this case, it makes more sense to dial in a longer attack time and shorter release time. Depending on how much of the quieter information you want to be pulled up, a short to medium release will do the trick. You may even want to bump the ratio up higher to bring out some exaggerated pumping and intentional distortion—in the case of parallel compression, this isn’t always a bad thing!

Keep in mind that the compressed version of your audio is simply there to round out the uncompressed version, instead of to shine as a standalone element. So, don’t be afraid to really clamp down with your compressor to make sure you’re getting all the benefits of running things in parallel.

3. Not EQing your compressed signal

To get additional control over your processed signal, there’s nothing stopping you from using EQ on parallel compression returns. If you want a really beefy low-end, say in a drum kit, try a boost around 100 Hz to exaggerate the attack of the kick or snare. Placed before the compressor, this will drive it to clamp down harder and alter the overall tone, which can be a desired effect. Cutting or boosting with EQ after the compressor allows you to sculpt the signal further to better fit the mix.

You can also get some interesting results by using a detection filter in your compressor. When activated, the detection filter in Neutron’s Compressor module allows you to set the parameters for both a low pass and high pass filter that your signal will run through before hitting the compressor. This lets you further hone in on the frequencies you want to allow to trigger the compression, as well as defines which frequencies will be affected by the Compressor module.

Use the detection filter in Neutron’s Compressor module when doing parallel compression
Use the detection filter in Neutron’s Compressor module when doing parallel compression

Neutron’s Compressor module also allows for multiband compression, so you can split up your signal into custom frequency ranges and assign different compression settings to each. You might want to bring up the lows, but have the compressor work harder on some mid and high range resonance to prevent disrupting the mix balance when blended in.

The bottom line here: EQing your compressed signal can yield some really amazing results when using parallel compression. As for how and when in your signal chain you add the EQ, that’s up to you!

4. Getting fooled by level

Parallel compression increases the level of your mix—you’re adding another track of audio to your mix, after all. Since we have a preference for louder over quieter, it's hard to know whether the decisions made in parallel are improving your mix or just playing to our natural bias.

To get a better read on this, I fade my compressed track into the mix until the original signal starts to feel rounder and more powerful without getting much louder. If you take away the compressed signal, it should feel like your mix is missing something, but not necessarily sound quieter.

As a new mixer, you may benefit from a metering tool like Insight that provides visual feedback on the levels and loudness of your mix before and after parallel compression. While bringing in the compressed signal, monitor the readout displays to gauge how much of an increase it brings. If the dials heat up and this isn’t your original intention, you may want to bring the compressed signal back down and re-evaluate your approach.

5. Sending the entire signal to be compressed

In a parallel setup it might be appropriate to send your entire signal to a compressor return, but this isn’t always the case! For example, if you only want to beef up the kick and snare, send only those sounds and leave the rest untouched—this is another purpose for using the detection filter in Neutron’s Compressor module.

When mixing live drum kits, room mics and other ambient material will start to splatter when you heavily compress them in parallel, especially if some compression was already applied to the “dry” signal for consistency. Again, this isn’t a set rule, and there may be certain sections in your song where bringing up the room in this way will give you a more lively sound.

Use a similar thought process when sending a signal with time-based effects to a compressor return track. A big reverb or delay will surely change the way your compressor acts, and may lead it to trigger when you don’t want it to.

6. Using it all at once

The stealthy quality of parallel compression can lead us to believe it’s the secret sauce that will take our mixes to the next level. As a result, we start to overuse it and apply it in big slabs all over the place.

I’ve found some more interesting results (and had more fun getting there) by dialing up parallel compression in smaller amounts at various stages in a signal path. You may want to use one compressor at the instrument level for distortion and another for warmth, then add a third on the related submix for level, or even on the master output.

Give this a try in your own mixes. Do your drums, vocals, and whatever else sound best when you apply parallel compression in one go? Or does a more splintered approach give you the desired sound?

Start using parallel compression

There are many benefits to using parallel compression, but like all techniques, there are also pitfalls. The tips in this article should give you a clear idea of when you’ve fallen into one of these traps and how to get out.

Start your free trial of iZotope Neutron to experiment with all of these parallel compression techniques in your mixes. 

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