If you're recording music with a computer, and unless you're recording traditional music, once you've got the basic noises committed to your hard disc you'll probably find that they are a tad 'flat'. This is where audio effects and processors come in: they're used to make music sound better.

All of these effects and processors can be used subtly, either to tweak an instrument sound or help a mix hang together, or they can be pushed to extremes for creative perversion. The best way to see what they can do is to dive in.

Effect or Processor

There is an important difference between effects and processors. Basically an effect is something you add to a sound whereas processing is something you do to a sound. It's generally better to apply processing before effects. This is because many processors affect the dynamic range of the signal and if an effect is applied before processing the result can be far from that intended. Having said that: if you're making music there are no rules so, if it sounds good, go with it.

Processors

Gating

A gate is intended to reduce noise on a recording. Put simply: when the signal drops below a certain level (the threshold) the gate will close, stopping any sound (including noise) getting through. When the signal goes above that level the gate will open and the sound gets through. In addition to a control for the threshold there are usually controls for attack and release which set the speed that the gate opens and closes respectively.

Gates can also be triggered by an external signal so, for example, you can put the gate on a bass guitar part and trigger it with the bass drum to tighten them up. The same technique was taken to extremes in early electronic dance music when a percussion/drum part (such as a hi-hat) was used to trigger a gate on a synth pad (such as a string part) resulting in a 'chopping' sound. The Shamen used this extensively.

Compression/Limiting

Equalisation

At it's most basic an equaliser (EQ) is nothing more than a volume control but, rather than changing the volume of the whole sound, it only affects a specific center frequency and a small range around it. The most common are those found on domestic audio equipment but they come in many different and increasingly complicated types:

• Fixed Equalisers. These are the most basic type of equalizer as the knobs will only adjust the level of a specific frequency range, which cannot be changed. The most obvious example is the EQ on a hi-fi amplifier where you have one knob for the bass and one for the treble. They're not much use in recording as they tend to cover a large frequency range so any adjustment will affect a large part of the sound.
• Sweepable Equalizer One step up from the fixed EQ, a sweepable EQ has two knobs for each frequency range (amount and frequency) so that you can not only change the level of the frequency but also change the center frequency you're affecting. This gives a lot more control: if you need to adjust something you can pick the frequency you need rather than the one you're given.
• Parametric Equaliser The most flexible EQ of the lot, a parametric EQ allows you to change the level, frequency and the bandwidth ('Q') that you are affecting. Even though a sweepable EQ allows you to change the frequency you are still stuck with the bandwidth you are given so, if you need to reduce the signal at 1khz you might find that everything from 500hz up to 1.5khz gets affected too. With a parametric EQ you can adjust the bandwidth so that you only affect the signal at 1khz. Alternatively you can open it up to cover a wider frequency range. This gives you a lot of control.

These first three tend to appear in combination with each other. It is rare to find a fully parametric EQ: usually you'll find a fixed bass and treble EQ with two parametric, or at least sweepable, midrange EQs together. Having said that, when using software the available options tend to be more flexible.

• Graphic Equalizer. Found on everything from domestic hi-fi to top of the range studio equipment a graphic EQ can look pretty daunting but is actually quite straightforward. Using sliders rather than knobs, a graphic EQ acts in the same way as bass and treble controls but acts over a larger range of frequencies, with one slider for each. Domestic graphic EQs usually control five different frequencies but professional versions can regularly control up to 128 per channel. That's 256 sliders. While they might look scary you need to remember that it's just one basic volume control per range of frequencies.

Usually the fixed, sweepable and parametric EQs will be used while recording and mixing in order to tailor the individual channels' sounds. The graphic EQ tends to be used over the whole mix to help give an overall tonal quality.

Effects

Echo/Delay

This is pretty straightforward in principle but can have stunning results. An echo simply copies a sound and repeats it. The most simple use is to add depth to a sound, whether as a short echo¹ or with a longer delay. If used in these ways the volume level of the echo should be kept quite low to avoid cluttering the sound. Things get more interesting when the echo is used rhythmically. By setting the echo to be in time with the music (something most software will do automatically) interesting times await! When used in conjunction with rhythmic gating you can create huge washes of lush, bubbling, funky sound. Try setting it to triplets and have some fun.

Reverberation

Imagine you're a large cave and you clap your hands. You'll hear the original clap and some echoing but the sound will seem to decay slowly away. What you're hearing is reverberation (reverb). Basically reverb is a collection of echoes which are too short for the mind to separate so they merge into one long sound. Your software will probably have different types of reverb such as Chamber, Room, Cathedral etc. These are meant to reproduce the effect of playing in their respective spaces, but you don't have to use it realistically if it's not appropriate. A classical guitar solo might benefit from a touch of 'Church Hall' but the intricacies are likely to be lost in the midst of a Chemical Brothers style synth and drum loop extravaganza.

A word of warning: Reverb is very easy to overuse. In isolation pretty much any noise will sound better with a wodge of reverb on it but you have to be careful: too much reverb in a mix will make everything sound distant and indistinct.

Chorus/Flanging/Phasing

Ring Modulation