Compression is one of the most used dynamics processors in recording and mixing.
To compress your acoustic, clean, and distorted guitars in Garageband, use the presets, “Acoustic Guitar,” “Guitar Electric,” and “Crunch Guitar” respectively, that way you have a great jumping-off point, as well as an introduction to the parameters of the compressor and what they sound like.
Technically, compression increases the volume of the quietest sounds and decreases the volume of the loudest sounds. For this reason, it’s incredibly useful in the world of music recording and production.
For a full explanation of the compressor and its parameters, I recommend checking out my illustrated guide to compressors at this link here.
While you should certainly take a look at the aforementioned article, it’s worth quickly running through the parameters of the compressor for the sake of this article, and I’ll show how its settings can be applied to the guitar.
There are 5 main parameters of the compressor:
1) Threshold – the point in dB at which the compressor starts functioning
2) Ratio – how much the compressor is reducing or increasing the loudest and quietest parts of the song, or in other words, the strength of the compressor
3) Attack – how fast the compressor latches on to the audio signal
4) Release – how fast the compressor lets go of the audio signal
5) Gain/Output Level – the total strength or volume of the audio signal
Compression has many different functions including emphasizing the smaller details of sounds; making sounds thicker and fatter; adding warmth; equalizing volume levels; balancing levels; making everything louder; softening or accentuating dynamic changes; increasing “punchiness;” decreasing or increasing subtle sounds; emphasizing lost dynamic changes; moving the position of the sound in the mix forward or backward; making music sound more natural, ducking, and more.
Now that we’ve explained the basics of the compressor, as well as some of its functions, let’s dive into how this can be applied to a guitar part.
Typically, the purpose of using a compressor on the guitar is to add balance in volume to the notes played on the guitar.
While an amazing player might be able to play the guitar in such a way where each note is plucked evenly and with the same amount of strength, the truth is there might be some imbalances.
This is where the compressor comes in.
We can use it to essentially equalize the volume of all the notes played, that way if the guitar player played a note on the low E string a lot louder than a note on the high E-string, we can make them closer to each other in volume (amplitude).
It’s almost as if we’re literally smoothing out the audio signal, ironing out the lumps, so to speak.
While a total increase in volume to the guitar track will bring up the volume of the desired part, it will also increase the loudest portion of the track, which means there will be an undesirable imbalance in volume.
How To Set Each Parameter Of The Compressor on Guitar
Like nearly every other mixing process, how we go about setting the parameters depends on the purpose of why we’re using a particular processor or FX plug-in.
First things first, when setting the Threshold setting, it’s a good idea to take a look at the VU meter setting which will inform you in your decision of setting the Compressor’s Threshold.
Typically, you want to have a bit of headroom, so it’s good practice to keep all of your tracks at least below -5dB. After you’ve set up the volume of your guitars, you can set the threshold appropriately.
If we wanted to even out the quiet and soft sounds of the guitar, a good practice is to set the threshold between -12dB and -22.0dB.
The lower we set the Threshold on the guitar’s compressor, meaning, toward -50dB, the larger the amount of the guitar’s signal we are compressing.
In the image below, the lines are meant to illustrate where the threshold has been set. Any signal outside of the black, red, or blue lines will be decreased, and what’s within the lines will be increased in volume.
By how much is determined by the ratio setting, which we’ll get into shortly.
In other words, if we set the compressor’s threshold to -50dB, what we’re doing is we’re adjusting the volume of nearly every part of the guitar signal, which is usually too much.
A better thing to do is to set the threshold to around -22.0dB, that way we’re decreasing only the loudest part of the guitar’s signal, and slightly increasing the quieter sounds, rather than squashing the entire sound.
In other words, if we’ve set the threshold to -50dB, we’ll straight up squash the signal, especially if the ratio of the compressor is set to around 4:1 or higher.
On the other side of the aisle, if we set the compressor’s threshold to +0.0dB, then we’re compressing probably nothing.
Go ahead and set the threshold to around -50dB, you’ll notice that the compressor makes everything the same volume exactly, to the point of ruining the dynamic, and if you set it to +0.0dB, it’ll do nothing.
To compress only the loudest and quietest parts of the guitar, set the threshold low, in the -20dB range.
In the case of heavy metal guitars, we might approach this differently.
Heavily distorted guitars typically don’t need that much compression because they’re already saturated with the distortion which has the effect of thickening everything up, however, compressors are still used in heavy metal (and in pretty much every other genre as well).
If you take a look at an audio file for a heavily distorted guitar and compare and contrast it to a clean guitar file, you’ll notice that the wave format looks a lot thicker and consistent in comparison to the clean guitar.
Clean Guitar Image
Heavily Distorted Guitar Image
The ratio, as I’ve explained earlier in the article, is by how much we’re compressing the signal after it’s exceeded the threshold.
As a general rule, understand that when a ratio is set to 10:1, that means we’re essentially limiting, rather than compressing because when the signal exceeds the threshold, it’s been folded down enough where there are almost no other signals exceeding the threshold anymore.
Normally, a good starting point when setting the ratio is to hover around the 4:1 range.
2:1 = Low Compression
5:1 = Medium Compression
8:1 = Strong Compression
10:1 = Limiting
Logically, it’s easy to understand the idea that the higher the ratio is set, the more compression is applied.
Taking a look at the image below, you can see the comparison between the ratios.
A ratio of 2:1, is literally cutting the signal in half outside the threshold
A ratio of 4:1 is cutting the signal into quarters outside of the threshold
And a ratio of 8:1 is cutting the ratio into eighths outside of the threshold, and it continues on and on.
If the threshold is set to -20dB, and our ratio is 2:1, that means that whenever the signal exceeds -20dB by 2dB, it’s now being reduced to 1dB outside of the threshold.
If the ratio is set to 5:1, that means that if the signal exceeds -20dB by 5 dB, it’s reduced down to 1dB outside of the threshold. In other words, the ratio is kind of like setting up how much the signal is folded.
The higher the ratio, the more it’s being folded. I hope that the images above illustrate how the signal is kind of being folded.
The ratio setting on a guitar’s compressor will never be that high. Typically, the ratio should float between 2:1 and 5:1, and should rarely go much higher than that from my experience, however, it depends.
The Link Between Threshold And Ratio
Decreasing the threshold means that we’re increasing the amount of compression, whereas decreasing the ratio means that we’re decreasing the amount of compression.
Making adjustments to these parameters are typically done in combination with each other, so if we lower the threshold then we’ll also lower the ratio as well, and the same thing could be said when we’re increasing both of them.
The key idea behind this fact is to understand that lowering the threshold, which means more compression, and lowering the ratio, which means less compression, will end up with the same amount of total compression, although the sound will ultimately be different.
Explained in another way, a lower threshold means that more of the signal is affected, but a higher ratio means that more of the signal that is already being compressed is compressed even more.
Typically, the Attack is set up fast on the guitar, that way it quickly latches on to the signal and adjusts the level of it accordingly. Moreover, the attack is often used on the guitar in such a way to reduce the sound of the picking.
For instance, you can set the attack very fast, to around 20ms or so, just to see how it affects the sound of the pick hitting the strings.
The same thing could be said for more percussive instruments, which is usually the context in which the compressor attack is discussed.
If we want to soften the sound of some more abrupt instruments, such as the snare or other very loud instruments in which the signal is suddenly loud, then a much shorter (faster) attack is needed.
In other words, the longer the attack is set up, the more of the instrument’s natural attack is present. However, a natural attack on the instrument is not always desired.
Some people might ask why not just set up the attack time of the compressor to retain as much as the natural attack of the instrument as possible?
If we were to set it up so the natural attack is retained as much as possible, it would effectively render the process pointless, because there would basically be no volume reduction on the instruments at all.
Gain – Output Level
The Gain on the compressor is the easiest parameter to use on the entire compressor, because it simply acts as the “make-up gain,” or the volume control.
Whenever we compress a signal, there is a loss of volume somewhere along the line.
What you can do when compressing the guitar, or any instrument for that matter, is to turn the compressor on and off while adjusting the make-up gain to match the before and after volumes.
I like to normally increase the volume of the instrument, so I make sure there is some make-up gain set-up. It really depends on the instrument.
In the case of the latest song I worked on, I had the Make-Up Gain set to +1.0dB, that way there was a little increase in volume whenever I turned the compressor on and off.
Where To Place The Compressor In The Signal Chain
In terms of the signal chain, you typically want the compressor to come before all else with the exception of the noise gate, especially in the case of a guitar tone with reverb, delay, wah, and other effects.
However, it also depends on what you’re going for.
If you think about it logically, this is what makes the most sense, because the compressor allows us to shape the volume of all of the guitar’s signals, therefore, we don’t want to add the compressor after the reverb and delay, because then we’ll be compressing the sound of the reverb and the delay, rather than just the guitar.
It’s a good practice to use the compressor before, and then the FX after, that way when we apply the FX, we’re applying them to a signal whose dynamics are already at the level we want.
The same thing could be said for the distortion as well. We want to add the distortion to the sound after it’s already been compressed, but with some exceptions.
In the case of using a compressor on a distorted guitar sound, after the distortion in the signal chain, then we have to be more careful with how we set both the threshold, ratio, as well as the attack and release.
For instance, if we’ve cranked up the threshold and ratio on the distorted guitar signal, a consequence of this might be that we’ve also increased the volume of the distortion rather than the guitar’s natural sound. In terms of how this will sound, it’ll sound messier and fuzzier.
Moving on to the next part of the tutorial.
In this part, I’m just going to show you some of Garageband’s presets that I’ve modified a little bit, and I’ll explain what I changed and why.
Compressing Acoustic Guitars
*Track Volume set at -15.0dB
This is a pre-set I created that’s built off of Garageband’s “Acoustic Guitar” pre-set.
The only thing I’ve changed here is the gain and the attack. I increased the gain by 3.5dB and I also dropped the Attack down to 20 milliseconds, rather than 80 milliseconds.
The reason why I changed the attack down to 20ms, is because I wanted to reduce the sound of the pick hitting the strings.
In terms of the gain, I increased it by 3.5dB just to ensure there is somewhat of an increase in volume.
Go ahead and experiment with this pre-set on your acoustic guitar track, and oscillate between 80ms and 20ms, and notice the way in which it affects the sound of the pick plucking the strings.
Compressing Clean Guitars
*Track Volume set at -19.0dB
The original pre-set has its gain set to +1.0dB and the threshold set to around -22.5dB, however, I changed the threshold and the gain just by a little bit because I just wanted to bring a bit of volume balance to the guitar track.
This one is based on the “Classic Guitar” preset.
Compressing Distorted Guitars
*Track volume set to -12.5dB
In this case, I used the “Crunch Guitar” pre-set, however, I increased the threshold, ratio, and the gain, that way it evened out the sound entirely.
Typically speaking, the more you drop the threshold closer to -50dB, the more of the signal you’re compressing, and the higher the ratio, the stronger the compression on the signal that’s being compressed, and then you use the gain to make up for the volume that was lost in the compression process.
YouTube Video Tutorial
That’s all I really have on this topic for today. At some point in the future, I’ll revisit this topic again and add a ton of tricks, pre-sets, and other important things that I’ve learned.
It’s really up to you to experiment with many of these things and figure out what works for you.