Lessons, Music Technology

Basic Introduction to Effects and Processing

The Edge from U2 famously uses lots of effects to create his famous guitar sound. Watch him talk about how sometimes the effects he uses contributes to his sound in the video below.

One of the most commonly asked questions when starting to study Music Technology is about how you can identify effects and processing in your listening. A knowledge of effects and processing also helps you at Music GCSE, particularly in study of popular songs.

All of the audio samples below play the clean version of the synth riff, followed by the effect.

Dynamics Processing

Compression – reduces the dynamic range of audio, creating a more consistent volume level. Often used to help a part such as a lead vocal, cut through the mix. Sidechain compression is often used creatively in dance music to make synths duck in time with the kick drum.


In the audio sample below, the synth is controlled by a compressor with a sidechain linked to a four to the floor kick drum.


Noise Gate – removes or silences quiet sounds below a threshold. Often used to remove noise or quieter sounds between musical phrases, or to remove hiss/hum from a distorted electric guitar between phrases, so the gate opens when the guitarist starts to play.

noise gate diagram

Key Effects

Delay – creates a repeat of the sound. The feedback alters the number of repeats, and the delay time changes how long between each one. It is possible to synchronise delays so they play in time with the music. The picture below shows a plugin recreation of the Roland Space Echo Tape Delay.




Reverb – simulates the sound and ambience of being in a room. Can be excessively used to give the sense of being in a very large space. If there is no reverb, we can say that a sound is very dry. In the 1980s, gated reverb was commonly used, which used a dense reverb along with a noise gate to cut off part of the reverb tail, giving greater clarity to the mix.


The photo below shows a NanoVerb digital reverb unit.


Modulation FX

Modulation effects all depend on changing a parameter of a sound over time; for example, combining a signal and a delayed version, or changing the pitch according to another wave. We can use a LFO (low frequency oscillator) to do this. An easy way of identifying modulation effects is listening for a ‘wobble’ of something – does something change over time to create a sense of movement?


A chorus effect combines a wet and dry signal (with and without effect). The wet signal is slightly delayed and detuned, which creates a ‘shimmering’ effect that simulates multiple instruments or doubling, like in a choir or ensemble. Chorus is commonly used on guitars.



On a flanger, the dry signal is combined with a wet signal on which the delay time has been modulated. This gives a ‘whooshing’, ‘aeroplane’ effect, especially if the feedback is turned up high.



A phaser combines a dry signal with a wet signal on which an all pass filter has modulated the phase according to the incoming frequency. This means that phase cancellation takes place, altering the frequency content of the wet signal.



Vibrato is when the pitch of a sound is modulated. It is similar to the effect musicians use when playing a woodwind, stringed or brass instrument, or when singers sustain a long note. The vibrato effect in the audio sample below was created using a Rotary speaker emulator.



A tremolo effect is a modulation of volume. The volume is quickly ‘turned up and down’. This can be done in time with the music on a DAW.

EQ and Filtering

HPF – stands for high pass filter. It lets the high frequencies pass through, removing low frequencies below the cut off. Commonly used in dance music to give a ‘trebly’ sound.


LPF – stands for low pass filter. It lets the low frequencies pass through, removing high frequencies above the cut off. It is commonly used in dance music to give a ‘muffled’ sound.



It is common in dance music for producers to automate the cut off frequency and add some resonance to create a moving filter effect. The audio sample below has an automated cut off frequency that slowly removes a low pass filter. The filter is slightly resonant (it sounds whistly as it moves). The graph below shows a resonant low pass filter.


Guitar FX


Distortion occurs by turning up the volume of a sound too loud. We call this the gain, to differentiate it from the output volume.



Many digital distortion plugins hard clip the sound as in the diagram above. Guitarists sometimes prefer the sound of valve amps, which don’t clip the wave as harshly; we call this soft clipping, and it is often described as a ‘warmer’ sound.

Another form of distortion that occurs when using lower bit depths and sample rates is bit distortion. This is audible on old samplers and can be applied to synths and other instruments to create a ‘lo-fi’ sound.


Wah Wah

Wah wah is an onomatopoeic effect that changes the frequency content of a guitar. It is essentially a band pass filter with a moving centre frequency or a resonant low pass filter with a moving cut off frequency. It sounds like it is said!

Test Yourself

Can you identify all of the effects in the audio file below? They are played one after another; clean then effect each time. Use the link below to check your answers.





1. Tremolo

2. Vibrato

3. LPF / high cut EQ

4. Compression

5. Gating

6. Phaser

7. HPF / low cut EQ

8. Delay

9. Flanger

10. Chorus

11. Reverb