In some modern hi-fi equipment or digital music players you may often hear the phrase 'graphics equaliser', and perhaps if you have bought an electric guitar and use a well equipped amplifier unit, you may have graphics equalisation as an option included. But what is graphics equalisation, and in what ways does it affect the performance or sound made by an electric guitar?



The notes of a guitar are produced in response to assigned frequencies, with each frequency relating to a different note in the scale. Higher frequencies produce higher pitched note, with the lower notes being made through low frequencies. This is in much the same way that a string which vibrates very quickly produces a higher pitched sound than a string that is perhaps longer, or thicker, and vibrates more slowly, producing a lower note. Of course, with electric guitars the frequency is calculated electronically, as the vibration of a string actually does not cause the note to be heard. Instead, it is the electric magnetic field created by the string moving next to the pickup.

The frequency of a note can be manipulated and edited in a range of ways, and a graphics equaliser takes each frequency and can apply various effects through the manipulation of parameters, perhaps altering the fixed centre of a frequency, or creating fixed widths.

Distortion effects can also be created through graphics equalisation, by capping the frequencies generated. The equalisation process can be applied either as part of the guitar itself, with pedals or levers included that alter the signal sent to the amplifier, or as part of the amplification unit itself.

Where equalisation is used with a foot pedal, a number of effects are typically introduced, such as 'wah', 'auto-wah' and phase shifter. A wah-pedal is one which id operated by the guitarist using his feet, and the pedal generally rocks backwards and forwards, producing a scale of distortion, rather than simply switching it on or off. This scale can affect the frequencies in an almost analogue fashion, ranging from low frequency distortion to higher frequency distortion. This 'wah' effect actually makes the guitar almost sound as though it is making this sound - quite nasal, with an open mouth. The name comes directly from the way in which the guitar's voice sounds like someone actually saying the word 'wah', and is immediately identifiable. This effect is most typically found used in 1960s rock and funk music from the seventies.

In the sixties and seventies the wah-pedal often had a fuzz box incorporated. This applied the fuzz effect to the sound before the wah effect was added, creating an even more distinctive form of distortion known commonly as fuzz-wah. Many of these effects have names which sound very similar to the voice which the guitar makes when they are applied, and in this way the sounds and tones are instantly identifiable. Some of the most common wah pedals that are available include Dunlop's Cry Baby and the VOX V847 Wah.

When it comes to electric guitar effects, you will often hear the word voice used when describing the sound of the guitar itself, and many of the effects are named after sounds which could be made by the human voice, and which are similar. Thinking and describing a guitar's sound as like a voice does create a remarkable number of similarities, and makes a lot of sense when you listen to the sounds and effects generated.