Compression

Compression is probably the most widely used, and most misused, of all effects. Used correctly, it is a wonderful tool for both live playing and studio work, tho it is used in different ways for these two applications.

First we will look at use in normal playing situations. Probably the biggest use for compression is for getting more sustain. No lead guitarist believes there is any such thing as too much sustain, but getting *enough sustain is the bane of many a musician. Now, any instrument, by nature of its construction and materials used, is only capable of achieving a set amount of sustain, no matter what you do. But compression can lend some apparent sustain. You'll understand why I say apparent in just a moment.

It helps to think of a compressor as an "automatic volume pedal." What it does, in essence, is take any signal with a dB level over a specified level, or threshold, and reduces it by some amount (more on this later). Conversely, any signal below a set level will be raised by a certain amount. Try this experiment. Go grab your guitar and sit next to your amp. Hit a note and let it ring. You will notice (and I am sure you have noticed before) that after a short time, the note begins to decay, or get quieter, and die out. Now, hit the same note again, but this time, when it starts to decay, slowly turn the volume up. The note will seem to sustain for a much longer time. In actuality, the note had the same sustain each time, but when you turned up the volume, you could hear it longer. This is precisely what a compressor does.

In the studio, compression is used much differently (I also explain how to effectively apply compression to a rhythm guitar in normal situations, but since they are similar, I will group them together). I think it is important for you all to know this, since I am sure many of you do some home recording, and this could save you some frustration.

Picture this: 2 am, inspiration strikes. You plug into your handy-dandy portastudio and start rockin' out, and you get a beautiful take. Soft to hard, hard to soft, with flawless transitions between. You know you will never be able to play this piece like this ever again. Problem is, your level ranges from -5dB to +12dB. It sounds great, though.. Until you try to mix it with other instruments and find that in one part, it is too quiet, and in the next, too loud. So, you spend the next six hours riding the faders, turning it up and down so it will mix well (ironically, this is called finger-compression, and a similar situation led to the invention of the Compressor).

Remember that earlier I called the compressor an "automatic volume pedal," or in this case, an automatic fader. So, being the genius you are, when inspiration struck at 2 am, you thought ahead, and set a compressor with a threshold of +6dB, so that every time you would have hit that +12dB peak, it was lowered to +6dB. Not only that, but because you set the compressor, the lower frequencies didn't drown out the high end (VERY useful for rhythm guitar). And because you were such a genius and set the compressor, when you tried to mix, it went without a hitch. You came out with a perfect mix, and you end up getting a major record deal, and overnight you are a household name. Parents buy your cd for their toddlers, the high schools see an all time low in violence because they are all listening to your killer chops and saying, "hell YEA!" and Steve Vai asks if he can open for you.

Ok, ok.. Maybe that's a little far-fetched, but you get my point. If used correctly, a compressor can give you that dynamic control that will save you a lot of stress and premature balding, as you wont be pulling all your hair out.

Now, before I go on... I have to warn you. If used incorrectly, a compressor can be your WORST enemy. Compressors are commonly called "limiters," because, that same dynamic control you loved so much when recording, also sapped some of the dynamic nuances that give your instrument that human touch. If you set it too high, you will get a dynamic range of about 2dB, resulting in a tone that is sterile and mechanical. You don't want that. As a general rule, the goal here is transparency, you want to get your desired effect, while making it sound like you aren't using a compressor. It is vital that you understand this... like I said, a compressor can be your worst enemy if you don't know what you are doing.

Ok, having said that, and clearing my conscience, I can continue with the fun stuff. If you experiment with a compressor, you will find it is capable of some very cool things. First of all, many effects units (like anything from ART) benefit from the consistent signal provided by a compressor. But it can also be used to do some fun stuff. Using a compressor, it is possible to get controlled feedback with virtually no distortion (Adrian Belew uses compression in this way quit a bit).

So, now that I have told you all about what a compressor can do, it's time to explain how to do it. Most compressors have four different control types: ratio, threshold, attack and release, and input/output.

Let's start with ratio. This control sets the proportion for compression. This is usually displayed, "2:1," "4:1," etc. For example, say you have the compressor set with a threshold of +6dB, and a compression ratio of 2:1. For every two dB over +6dB, only 1dB well be let out. With 4:1, for every four dB above the threshold, only one gets out. The higher the first number, the more compression. Most compressors can also be set for "limit," meaning that any signal stronger than the threshold will be reduced to the level of the set threshold. In this case, with the threshold set at +6dB, a signal of +20dB would be compressed to just 6dB, there is no ratio, it just makes a wall.

Threshold sets the point of loudness where the compression kicks in, expressed as dB. Continuing with the previous example, with the threshold set at +6dB, any single above 6dB will be compressed at the set ratio, while anything below will be compressed at a ratio of 1:1 (or 1dB out for every 1dB in, meaning no compression at all...).

Attack sets the amount of time that will pass before the compressor will "grab" a signal that exceeds the threshold. Release determines how long the compressor will affect the signal. As a general rule, the quicker the attack, the more dynamic control, and the longer the release, the smoother the sound. However, for the sake of feel, this isn't always true

The input/output control is perhaps the most important control. In the example of the 2am recording session, the threshold took care of your 20dB peaks, but what about the times when you were at -5dB? Well, the input control sets a point where everything below it will be raised to that level. The output will raise the overall signal coming out of the compressor, like a volume knob on an amp.

You have to be careful with the output control. Remember that the compressor doesn't know the difference between music and noise, so if you turn up the output, you also turn up the noise. It is very important that you have the input level set at a point where you get a good signal-to-noise ratio before turning up the output.

The most important thing to remember when setting the controls is balance. Remember that the goal here is transparency. Any time you change one setting, check to see if you don't need to change the others as well.

Now that you have read this and learned how to use a compressor, its time for the best advice I can give you. Don't listen to me. Don't listen to anybody. This wasn't meant to be rules on how to use it, just a small insight on how it has worked for others. As is the case with any piece of musical equipment, you have to setup everything so that it serves to better your individual sound. Play around with a compressor, make it work for you. I just hope that this has helped you to accomplish that. Keep on rockin'!!!