Acoustic guitars are wonderful instruments used in a wide variety of musical genres, playing many different roles. They also often benefit from the essential mixing process of compression. When it comes to compressing acoustic guitars, there are no simple step-by-step instructions; every mix is unique. However, there are certain considerations we should take into account when compressing acoustic guitars, 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 acoustic guitar. No procedures work 100% of the time, and every mix is unique in its own needs.
Here are 9 pro tips for compressing acoustic guitar:
- Know when not to use compression on acoustic guitar
- Consider the role of the acoustic guitar in the mix
- Err on the side of light compression to keep transients
- Compression for depth
- Think of EQ before or after
- Be aware of bleed
- Make room for the vocal
- Always A/B test
- Use your ears
Let's discuss each of these tips in more detail to give you important considerations when compressing acoustic guitar in your mixes.
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Know When Not To Use Compression On Acoustic Guitar
The first tip I have for you is to really consider whether compression is appropriate for the acoustic guitar(s) in the first place.
If the acoustic guitar performance was recorded with the song's long-term dynamics in mind, it might be the case that we won't need to compress its dynamic range to have it sit well throughout the mix. However, if the loudest parts of the acoustic guitar are too loud and/or the quietest parts are too quiet, compression can help smooth out these variances.
Furthermore, the original recorded signal of the acoustic guitar is likely to be the most natural sounding. Of course, we can clean up issues of noise and resonance with EQ. However, applying compression can lead to slight-to-overbearing degradation of the signal and make it sound less natural in the mix. So if you want an open, natural-sounding acoustic guitar, consider not using compression (or light compression if it's needed).
Also, consider the genre of the music you're mixing and the typical mix aesthetic when it comes to the entire mix and the acoustic guitars. A classical piece recorded in a beautiful room will likely not warrant compression. On the other end, a modern pop song featuring acoustic guitar may require significant compression to have it sit consistently in the mix sections where it's present.
Consider The Role Of The Acoustic Guitar In The Mix
The second tip I have for you is to consider the acoustic guitar's role in the mix. Is it a solo guitar performance, a singer-songwriter piece with guitar and vocals, a full-band situation or perhaps a pop song with a bit of acoustic guitar as an element?
If the guitar is the only instrument, we may want to maintain all of its dynamics by not using a compressor. On the other hand, a bit of compression can help tame its dynamics for smoother levels throughout the song. Heavier compression could also be used if that's the mix aesthetic we're going for (though it's generally best to use a more subtle approach to maintain a natural-sounding guitar).
In singer-songwriter mixes, we may want the guitar to sit a bit behind the vocal, and compression can help us to do so by taming down the transients. In general, taming the transient information of an instrument will have the effect of pushing it back in the mix. We'll discuss this a bit more in Tip 4.
In a full-band mix, we may need to use compression to keep the acoustic guitar present across the different sections of the mix. We should also consider the role of the acoustic in the song in question.
If it's an acoustic rock song, we may want the guitar more upfront with light amounts of compression. If the acoustic guitar is only an ornamental element in the song, we may not care as much about keeping its levels consistent with compression, or we may want to compress it harder to push it back in the mix.
The same ideas can be expanded to other mixes, whether they're sparse or dense. Consider the acoustic guitar's role and determine which compression moves (if any) will help fit the instrument into the mix.
Err On The Side Of Light Compression To Keep Transients
Compression acts to reduce the dynamic range of a signal by effectively turning down the loudest parts. The transients of the acoustic guitar generally represent these loudest parts.
In sound and audio, transients are momentary increases in amplitude that happen, in the case of an acoustic guitar, when a string is plucked, picked, or otherwise struck. The transients are the “attack” of the guitar's sound and contain a lot of harmonic energy that quickly dissipates as the string continues to oscillate.
The transients are important for giving us a sense of the acoustic guitar's full sonic character, so it's often best not to alter them too much with compression.
A light amount of compression, say 1 or 2 dB of gain reduction at the peaks, can help to make the levels more consistent without having too much of an effect on the transient information.
Furthermore, we can increase the compressor's attack time to allow some of the transient information to pass before reducing the gain. In doing so, we can potentially enhance the transient information of the acoustic guitar as the compressor will pass the initial transient before clamping down on the signal immediately afterward.
Be careful when adjusting both the attack and release times to avoid unnecessary pumping artifacts. If the acoustic guitar performance is very fast with many transients in succession, this technique can be difficult to pull off.
To learn more about compressor attack and release times, check out my article Dynamic Range Compression: Attack & Release Controls.
Compression For Depth
Compression can be used to create a sense of depth in a mix. This is accomplished primarily by smoothing out the transients of the signal. By reducing the transient peaks of the acoustic guitar, we give the illusion of pushing them further back in the mix.
This is because we naturally hear distant sound sources with subdued transients and closer sound sources with greater transients.
However, there is some amount of give-and-take here, especially when using lighter compression. By making the levels of the guitar more consistent (but without necessarily crushing the transients), we help to solidify its position in terms of depth.
For example, if the acoustic guitar is mixed hot, subtle compression can bring it a bit closer to the listener. Conversely, if the acoustic guitar is mixed quiet, subtle compression can help solidify its distance from the listener.
Check out my top tips for depth in the mix in the following video:
Think Of EQ Before Or After
Compressing before or after EQ is largely a matter of taste and is often subtle in the differences it provides. But, when it comes to nice, open, harmonically-rich acoustic guitar parts, we may want to consider, or at least experiment, with having compression before or after EQ.
In general, compression before EQ offers a cleaner, sharper result.
Compressing an acoustic guitar before EQ gives us less control over what the compressor reacts to but more control over the tonal balance of the guitar. Note that the EQ should be applied more sparingly here since the audio has already been smoothed out.
In general, compression after EQ will yield a smoother, warmer result.
EQing an acoustic guitar before compression lets us shape the frequency content more aggressively, knowing that the compressor will help smooth it out. It's also good to control what the compressor “sees” and reacts upon.
Since acoustic guitars tend to have a great range of harmonic frequency content, utilizing both EQ and compression can often help mix them perfectly into the mix.
For more information on EQing acoustic guitars, check out my article Top 11 Best Tips For EQing Acoustic Guitars.
Be Aware Of Bleed
If the acoustic guitar has been recorded by itself in a nice acoustic environment or you've recorded a clean DI signal through an acoustic-electric, you can skip this tip.
However, if the guitar was miked up and recorded at the same time and in the same space as the vocal and other instruments, we ought to be aware of the bleed from these other sources in the acoustic guitar's track.
Because compression reduces the dynamic range of a signal, it will have the effect of bringing up the quiet parts of the signal relative to the loud parts. This applies to the wanted signal (typically loud) and the noise or bleed of the environment (typically quiet).
So when it comes to compressing the acoustic guitar, we should be wary of any bleed and how we'll be bringing it up in the acoustic guitar track with compression.
Revisiting the previous tip, we can opt to EQ out some of the bleed, resonances or noise from the signal before the compressor to help reduce the amount of noise/bleed that is brought up by the compression.
Make Room For The Vocal
Frequency masking is one of the most common and problematic issues in mixing. It happens when two or more tracks compete in similar frequency bands and effectively mask each other in the mix. Neither track, then, is heard clearly as a distinct sound source. Rather, within the band of high competition, the tracks blend together and cause poor separation.
I have a YouTube video dedicated to frequency masking. Check it out here:
While EQ is perhaps the primary tool for tackling frequency masking, we also have a more technical compression technique for the job: sidechain compression.
Put simply; sidechain compression is the technique of inserting a compressor on one track but having another track control the amount of compression.
For more information on inserts, check out my article Audio: What Are Inserts? (Mixing, Recording & More).
The sidechain signal of a compressor is typically the same as the input/program signal (taken either directly before or directly after the gain reduction circuit (see feedforward or feedback compression). The sidechain signal is effectively converted to a control voltage that controls the gain reduction circuit (the dynamic range compression) of the compressor.
However, in the “sidechain compression” technique, we utilize an external sidechain signal to control the gain reduction circuit.
Here's a basic diagram of a feedforward compressor with a switch to toggle between an internal and external sidechain. Hopefully, it helps to clarify what I'm writing about:
So let's say the acoustic guitar competes too much in the mid-range with more important elements (the vocal is a common one, but another lead instrument could also be considered).
It's critical to get these elements working together well within the mix, allowing both to be heard as distinctive tracks without too much competition and frequency masking between them.
In this case, we try sidechain compression to attenuate the guitar slightly to make room for the vocal when it's present and have the guitar back to its original level when the vocal is not present.
To use sidechain compression, we insert a compressor on the acoustic guitar and set the vocal as the sidechain insert to compress the guitar whenever it's present.
When done subtly within the mix, the vocal can punch through a bit more without reducing the acoustic guitar's overall perceived loudness or presence.
Always A/B Test
If you've been following me for a while now, you know how much I encourage A/B testing when mixing. A/Bing an acoustic guitar's compressor on and off (on/bypass) is no exception.
A/B testing effectively tests two options (option A and B) and compares the two to make an informed decision on which is better.
Whenever we make any adjustments to a compressor acting on an acoustic guitar, it's worth A/Bing the compression against the original signal and listening to whether the compression improves the sound of the guitar in the overall mix or not.
When A/B testing, bypass the compressor and listen for about 10 seconds. Turn it back on and listen for another 10 seconds. Repeat the process and decide whether to keep the compressor, readjust it, or get rid of it.
The human auditory system tends to adjust to whatever we're listening to. When mixing, we can quickly lose perspective and our objective decision-making skills. As we adjust parameters to achieve balance and any other goals in the mixing process, we can quickly lose our frame of reference of what good acoustic guitar compression actually is.
So use A/Bing to your advantage when compressing the acoustic guitar in a mix.
If you're interested, be sure to check out my video on the top 5 A/B tests worth incorporating regularly into your mixes:
To learn more about A/B testing, check out my article A/B Testing & Its Importance In Mixing (With 5 Best Tests).
Use Your Ears
This tip may be self-evident. However, I thought it was necessary to include it in this list.
There are no cookie-cutter settings for compressing acoustic guitar or any other instrument, for that matter. It all depends on the mix, and it's vital that we listen critically when compressing an acoustic guitar to ensure it fits properly into the greater context of the mix.
The “ideal” amount of compression is highly dependent on how the acoustic guitar was recorded, how else it's processed in the mix, its role in the mix, the style of music being mixed, and the compressor being used. It's far too complicated to give any one-size-fits-all settings.
I have a YouTube video on the importance of mixing everything in the context of the mix (rather than in solo). Check it out here:
While I can give you good starting points and general advice, the best piece of advice I could ever give you when compressing acoustic guitar is to use your ears.
If the acoustic guitar compression doesn't sound good or serve the mix, either get rid of it, change the compressor being used, or adjust the parameters of the current compressor. Rely on your ears (along with A/B testing) to get the best results!
Other Compression Tips For Common Elements
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- 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:
Determining the best compressor for your audio needs takes time, knowledge and effort. For this reason, I've created My New Microphone's Comprehensive Compressor Buyer's Guide. Check it out for help in determining your next dynamic range compressor purchases.