Revision:Effects

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In music technology, an effect (FX) is a term used to define the alteration, enhancement or modification of a particular sound.

Chorus

Chorus is an effect that modifies the sound of a single instrument to simulate a group of the same instruments.

Compression

The main function of a compressor is to reduce the dynamic range of an audio signal or a live performance so that it will fit into the fairly narrow dynamic range of recorders, etc. Firstly, a threshold is established. When the audio signal is louder than the threshold, its gain is reduced. The amount of gain reduction applied depends on the compression ratio setting. For example, with a 2:1 ratio, for every 2 decibels the input signal increases, the output is allowed to increase only 1 decibel. A variety of other parameters in the compressor will also affect its performance processing specific signals - attack time, release time and others are very important.

Another way a compressor can be used is to make a signal's average level higher, such as evening out a specific instrumental performance or part, fattening up sounds or increasing the apparent sustain on an instrument such as a guitar.

Applying fairly heavy compression to a part is used to emphasise a 'breathy' sound quality. A compressor can also be used to eliminate any distortion.

Delay

Delay is an electronic device designed to store a signal for a specified period of time and then release it, therefore delaying the signal relative to other parts of an audio program. Delays are often used to create echo effects, where a particular signal may repeat several times, with each repeat being lower in level than the prior one.

Distortion

Distortion adds sustain and additional harmonics and overtones to the signal, creating a richer sound.

Proximity Effect

This is a distortion effect which increases the bass or low frequency response when a sound is close to a microphone.

Double Tracking

The process of recording a track, then recording a second track while listening to the first and duplicating it. When the two tracks are played back together, the result is a slight 'chorusing' and fattening of the signal due to minor pitch and timing differences between the two performances. Double tracking is an effective tool, and has been used extensively in most pop music styles.

Equalisation (EQ)

An equaliser is an audio device which equals the tonal characteristics of a particular sound. Creatively it is used to alter the relative balance of frequencies to produce desired tonal characteristics in sounds.

Applying no EQ settings retains the natural sample or recorded sound.

Flange

an effect applied to a sound wherein a delayed version of the sound is mixed with the original. An effect created by layering two identical sounds with a slight delay (1- 20 mS) and slightly modulating the delay of one or both of the sounds. The term comes from the early days of tape recording when delay effects were created by grabbing the flanges of the tape reels to change the tape speed.

Gate

This is a dynamics device whose function is to remove unwanted audio material below a certain threshold.

Modulation

The fast oscillation of one or more operators or sound waves of a synthesized sound. Commonly used in FM synthesis to add some complexity and texture to a sound. Many MIDI controllers and keyboards provide a specific wheel or slider for controlling the modulation of an instrument sound (often referred to as the mod-wheel). The process of one audio or control voltage source influencing a sound processor or other control voltage source. Example: Slowly modulating pitch cyclically produces vibrato. Modulating a filter cyclically produces wa-wa effects.

Modulation Index: The depth of modulation when performing frequency modulation.

MODULATION WHEEL - one of several common continuous controls on a MIDI device. Often used to add a vibrato effect to a sound.

Normalisation

Normalisation increases the gain of an audio file until its loudest point (or sample) is at maximum level.

Panning

The process of controlling the relative position of a sound in a stereo field during mixdown or recording using a pan-pot. Usually this is not completely effective as the pan-pot alters only the relative amplitude of the sound left to right and not the crucial time aspect.

Phasing

Reverb

The remainder of sound that exists in a room after the source of the sound has stopped is called reverberation, sometimes mistakenly called echo.

Comments

These notes are aimed at students studying GCE Edexcel Music Technology