Vocals are often the most important element of a song and mix, while compression is certainly one of the essential mixing tools. When it comes to compressing vocals, there are no simple step-by-step instructions; no vocalist, performance, or mix is the same. However, there are certain considerations we should take into account when compressing vocals, which is what this article is all about.
Before we go any further, I should state that there are no hard rules with compression or any other mixing process. The tips mentioned in this article are simply suggestions and techniques worth considering when compressing vocals. There are no procedures that work 100% of the time, and every mix is unique in its own needs.
Here are 11 pro tips for compressing vocals:
- Consider the role of the vocal in the mix
- Consider the genre
- Soft-knee for gentler, more natural results
- Serial compression for natural consistency
- Parallel compression for weight
- Reduce sibilance with multiband compression
- Using bus compression for glueing vocals together
- Enhancing transients on percussive vocals
- Don't be afraid of volume or fader automation post-compression
- Dynamic delay and reverb
- Compression for colour
Let's discuss each of these tips in more detail to give you important considerations when compressing vocals in your mixes.
Consider The Role Of The Vocal In The Mix
The first tip I have for you is to consider the role of the vocal in the mix. Are we compressing the lead vocal, a doubled lead vocal, a background vocal, or something else? Is the vocalist in the song meant to be upfront in the mix, or is the vocal meant to blend in with the rest of the instruments?
If the vocal is meant to be the lead element whenever it's present (which is often the case in modern pop genres), then we'll want to push the vocal channel above the other instruments.
When pushed above everything else, the dynamics of the vocal are exaggerated to the listener. A loud note or phrase of the vocal can become overbearing and even overload/clip the channel or mix, while quieter parts can become hidden under other instruments.
Therefore, we may want to consider a bit more compression than we may originally believe necessary to keep the vocal upfront without having great variations in volume.
With quieter vocals that blend with the rest of the tracks in the mix, we can often get away with less compression, allowing for more dynamics. However, we should still be aware of any issues where the vocal pokes out too much or gets lost in the mix. Compression can still help with these issues.
As for background vocals, which are often mixed low, we can also often go about compressing them more subtly than an upfront lead vocal. If there are multiple background vocals, it can be worthwhile to bus them all together and compress the bus to help glue them together into a more cohesive-sounding part of the mix.
Consider The Genre
In addition to understanding the vocal's role in the specific mix you're working on, it's also important to consider the genre/style of the music.
There are certain mix aesthetics that listeners have come to expect from certain genres of music. For example, an EDM hit will be mixed differently from a Country song, which will be mixed differently from a Metal song, and so forth.
Some genres are, generally speaking, more compressed than others. A Pop vocal, for example, is likely to be much more compressed and upfront in the mix than a Jazz vocal.
So keeping these “standards” in mind, we can err on the side of more or less vocal compression or even no compression at all.
Soft-knee For Gentler, More Natural Results
If available, try a soft knee compressor to clamp down on the peaks of the vocal. A soft knee can yield a gentler result that the often aggressive nature of peak reduction with hard-knee compression.
The knee of a compressor refers to the transition point around the compressor's threshold where the output becomes attenuated versus the input. A hard knee offers a more distinct triggering of the compressor, while a soft knee allows for a smoother and more gradual transition to compression.
Here's a visual example of a hard knee (to the left) and a soft knee (to the right) on input level (x-axis) vs output level (y-axis) graphs:
With soft-knee compression, the gain reduction will actually begin taking place just before the set threshold, and the full ratio will become achieved across a range of levels around the set threshold point (above and below the threshold).
So rather than the vocal suddenly getting compressed at the full ratio (according to the attack time) as it exceeds the threshold, which can sound a bit unnatural or obvious, we can utilize soft-knee compression to apply a smoother style of gain reduction to the vocal.
While the difference may be subtle, it's worth mentioning and experimenting with in your mixes and going with whatever option benefits the mix the most.
Note that some compressor plugins offer a continuously variable knee control, allowing us to dial in the perfect knee shape for our vocal compression.
To learn more about the knee of a compressor, check out my article Dynamic Range Compression: What Is The Knee Control?
Serial Compression For Natural Consistency
Serial compression, as the name would suggest, is having multiple compressors in series within a defined signal path. In other words, having a compressor's output feeding another compressor's input (and so on) somewhere down the line.
Serial compression could be as simple as inserting two compressors on a single track or having a single compressor on a track that's ultimately being fed through a mix bus compressor. It could involve many more compressors in any given signal chain (a track into a bus into a mix bus, etc.).
To keep things simple for this article, we'll discuss compressors inserted back-to-back on a single vocal track.
Serial compression, in this way, is great for not overloading any single compressor. It can sound more natural and shave off more dynamics, leading to more consistent vocal levels without as many unnatural pumping artifacts. We can also get different colours of different compressors (see tip number 11).
Imagine pushing 9 dB of gain reduction on a single compressor. Chances are the vocal will sound pretty “squashed” and unnatural. The transient information will likely suffer along with the sustain. Although it can be done in some mixes, it's typically a losing battle attempting to get that much gain reduction without these negative side effects.
However, if we were to utilize two compressors to compress 4.5 dB of gain reduction each, we'd be able to get more natural results. The first compressor would tame the peaks, and the second would help round out the remaining higher-amplitude moments.
What if we applied that same 9 dB of gain reduction over three compressors (3 dB of gain reduction each)? When done correctly, it would lead to even less pumping, giving us a more natural sounding compression and a more consistent sound.
Try this out for yourself the next time you need a significant amount of vocal compression to fit a vocal in the mix appropriately.
Parallel Compression For Weight
Parallel compression is a technique whereby two signals will be mixed together: one original track and one heavily-compressed version of the original track.
This technique is effective for giving weight and power to mix elements, including vocals, by acting as a sort of upward style of compression.
In other words, when the heavily compressed is mixed underneath the original, we get the weight of the squashed version along with the dynamics of the original. The resulting peak won't be attenuated (as the parallel channel is mixed lower than the original). Rather, the dynamic range will be reduced by bringing up the quietest parts of the resulting mixed signals.
The parallel compression technique requires a bit of routing. Here are the basic steps:
- Send the vocal to an effects return (this is the “parallel channel”)
- Insert a compressor on the return channel
- Set the parameters of the compressor so there's a heavy amount of compression (lots of gain reduction)
- Mix the return channel under the vocal to taste
When setting the parameters of the parallel channel's compressor, ensure the time parameters (attack and release) are set fast enough to ensure adequate pumping of the gain reduction. The key to the squashing effects of over-compression is making the gain reduction pump or “making the needle dance” when referencing a VU meter.
If, alternatively, we have slow time parameters that pin the needle down, our compressor will act more like a volume control than a heavy amount of compression.
To clarify with words, let's consider an example: If a compressor's set so its amount of gain reduction swings between 0 dB and 10 dB, it will sound very compressed. If a compressor's set so its amount of gain reduction swings between 9 and 10 dB, it will sound like it's only compressing 1 dB but with its output turned down 9 dB. I hope that makes sense.
So utilize parallel compression to thicken up a vocal and give it more weight and presence in a mix.
Reduce Sibilance With Multiband Compression
In many cases, multiband compressors can be set up to mimic, or even entirely copy, the signal flow of a de-esser.
A de-esser is a specialized style of compressor that acts to reduce the harshness of sibilants when they arise in the signal (most typically a vocal signal).
Phonetic sibilance is a vocal formant known as “fricative consonant,” in which the tip or blade of the tongue is brought up near the teeth or palette, and air is pushed past the tongue. It is better known as the hissing sound. In English, sibilance happens on the consonant sounds of S, Z, Sh, and Zh (as is “leisure” – lei-zh-ure).
Sibilance is critical for vocal intelligibility but can quickly become harsh and piercing if untamed in a mix. The general frequency range of sibilance ranges from 5 kHz to 8 kHz (though it may occur below or above that range).
Using a multiband compressor, we can isolate the sibilant range of the vocal in question and have relatively aggressive compression settings to tame these specific frequencies apart from the others.
If our multiband compressor has a global control or external sidechain capabilities, we may want to utilize the sibilance band to control the gain reduction of the entire signal bandwidth.
However we go about it, we can use multiband compression to ensure the sibilant issues are dealt with as they arise without overly affecting the other frequencies of the vocal.
To learn more about reducing vocal sibilance in a mix, check out my article Top 7 Tips To Reduce Sibilance In Microphones & Audio Mixes.
Using Bus Compression For Glueing Vocals Together
Buses (or “subgroups”) are invaluable routing tools when mixing. They can make routing and processing so much easier by allowing us to combine several instruments for bus processing and routing.
You may have heard the term “glue” when referencing compression. This is the effect the compression can have, especially on the mix bus, or making the elements of a mix sound more cohesive and “glued” together with each other.
This “glue compression” is one of several ways to make an entire mix sound more cohesive, which is the ultimate goal of mixing.
But using compression for the “glue” effect isn't only reserved for the mix bus. We can use it on vocal buses to great effect, too. This is especially the case for group and background vocals.
Set up a bus and route the outputs of the vocals to it. This could be all the vocals, just the lead vocals (plus ad-libs or doubled takes), background vocals, group vocals, etc.
Apply a gentle amount of compression to the bus and help tie these elements together to give a sense/perception that they belong together and exist within the same world.
Enhancing Transients On Percussive Vocals
Compressors are designed to reduce or “compress” the dynamic range of a signal. However, they can also be set up to actually increase the dynamic range or, at the very least, shape the transients of the signal.
Put simply; this is done with “longer” attack and release times.
The attack time is the amount of time it takes for a compressor to engage/react once the input signal amplitude surpasses the threshold. It's a rate of change whereby the compressor gradually reaches its full ratio over time. It's not a delay of action, where the compressor will clamp down fully after a set period of time.
The release time is the amount of time it takes for the compressor to disengage (to stop attenuating the signal) once the input signal drops below the threshold. Like the attack time, it's a rate of change whereby the compressor gradually disengages over time. It's not a delay of action, where the compressor will suddenly stop compressing after a set period of time.
So if we have a particularly transient vocal performance, we can apply compression with a slow release time to allow the transients to pass through uncompressed. We can then adjust the release time so that there's minimal pumping while allowing the compressor to disengage before the following transients.
This can be tricky with more complicated vocal rhythms and will likely take careful tweaking of the parameters to get just right. However, when done well, it can enhance the dynamics of an already dynamic vocal performance.
For more information on transient shaping and actually increasing the dynamic range with compression, check out my video:
Don't Be Afraid Of Volume Or Fader Automation Post-Compression
Considering the importance of balance in a mix, we can point toward the faders as the primary tools for adjusting the level balance between tracks.
Extending this idea of balancing with faders, we can imagine compressors as being automatic fader controls.
To explain, a compressor will apply gain reduction to a signal as that signal surpasses a defined threshold level. This is similar to manually pulling a track's fader downward as that track exceeds a certain threshold.
So, in theory, we could carefully and meticulously automate the fader (or some other control) to achieve the same effect as using a compressor. Of course, compressors are much more efficient, but this is a good way to understand the similarities.
With that, we can move on to this tip in more detail.
Because of the efficiency of compressors, it can be tempting to attempt to control the dynamics of a vocal with absolute perfection using only compressors.
While serial compression (multiple compressors in series) can help share the load of dynamics control to produce more natural results than overworking a single compressor, we still may have work to do post-compression to really hone in on controlling the dynamics of the vocal.
If we can't quite get the results we need from a compressor (or multiple compressors), we can often easily make up the difference with fader automation. This can lead to more natural results than forcing a compressor to do all the work independently.
If the vocal is still too loud in some parts and compression causes unwanted results in the rest of the vocal, we can utilize a simple automated fader move to bring the vocal down only in the part.
Conversely, if the vocal gets lost only in a few select lines during the mix, we can bring the fader up only in these sections rather than relying on more compression during the rest of the vocal.
We can also choose to automate the volume of the signal pre-compression by inserting a gain/trim plugin before the compressor on a track. Alternatively, we could utilize a bus setup where we can control the amount the track is sent to the bus with a knob or fader before compressing the bus.
Automating vocal levels before compression can help to feed the compressor with a more consistent signal, helping it to work less hard and yield potentially better results.
Dynamic Delay And Reverb
Vocals rarely sound amazing dry. It's most often the case that a bit of delay or reverb can liven them up in the mix and have them sit within the dimensional space of the mix.
While subtlety is often a great strategy for such time-based effects, there are also situations where pushing the delay or reverb a bit hot can be super effective for the mix at hand. The big issue here is that doing so has the consequence of drowning out the vocal (which is especially bad when it's the focal point of the song/section).
Dynamic delay and reverb to the rescue!
These techniques require a bit of routing and sidechain compression. Here are the basic steps:
- Send the vocal to an effects return
- Insert a delay or reverb effect on the return channel
- Set the parameters of the delay or reverb to taste (loosely if need be)
- Mix the return channel under the vocal to taste (typically hot enough to cause issues of drowning out the vocal)
- Insert a compressor after the delay or reverb on the return channel
- Set the vocal as the external sidechain control signal for the compressor
- Set the parameters of the compressor to taste (to make the vocal clear when its present and also have the delay or reverb present in between vocal lines)
- Adjust parameters and faders as necessary
Using this technique, we can ensure vocal clarity while the vocal is being played back while also having the time-based effect well represented in the mix between vocal lines.
Compression For Colour
In addition to the main purpose of automatic gain reduction, compressors will have the effect of colouring the sound. While some compressor plugins are programmed to be as transparent as possible, many other plugins, and certainly hardware compressors, will impart their own sonic imprint on the audio signals passing through them.
This colouration is sometimes experienced as an inherent EQ curve, though perhaps more obviously, it's experienced as harmonic saturation, where new harmonic information is effectively added to the signal due to the distortion of the components (or programming) of the design.
Such colouration can help to enhance the character of the vocals, and utilizing compression for its characteristic “sound” is commonplace. It may even be the case that we introduce a compressor in-line without even applying any gain reduction only to add colour to the vocal.
One issue to consider is the inherent noise caused by hardware compressors and analog plugin emulations. We must ensure proper gain staging to achieve a solid signal-to-noise ratio. This means we need to drive the compressor with enough signal level to avoid excessive noise relative to the signal while also keeping the signal level low enough to avoid excessive distortion.
On top of the inherent sonic characteristics of certain compressors, the actual gain reduction applied by the compressor will also obviously alter the sound. In this way, we can apply subtle amounts of compression to add a bit of extra character to the vocals as well.
Other Compression Tips For Common Elements
- Top 11 Best Tips For Compressing Kick Drums
- Top 10 Best Tips For Compressing Snare Drums
- Top 9 Best Tips For Compressing Electric Guitars
- Top 9 Best Tips For Compressing Acoustic Guitars
- Top 11 Best Tips For Compressing Bass Guitar
- Top 9 Best Tips For Compressing Pianos & Keyboards
- Top 11 Best Tips For Compressing The Mix Bus
Be sure to also check out my top overall 11 compression tips for mixing in this video: