Hi, I am Rasheeq Rayhan from Dhaka, Bangladesh. This lesson is for week 3 of

Introduction To Music Production at Coursera.org. I will be teaching categories of

effects including which plugins go in each category and which property of sound

each category relates to.

There are basically three categories of audio effects we use in the signal flows of

DAW (Digital Audio Workstation). The process is called DSP (Digital Signal Processing).

They are generally related to three of the principles of sound. They are:

1. Dynamic Effects

2. Delay Effects

3. Filter Effects

1. Dynamic Effects:

Dynamic effects play a crucial role in modern mixing. They are designed to alter the

dynamic range of an audio signal. They are important because they allow you to control

the ratios between high and low peaks in dynamic of an audio track over time. Dynamic

effects are related to “amplitude”.

These types of effects are more often used on live acoustic instruments than on

synthesizers and therefore their applications in a sequencer/MIDI environment is

somewhat limited.

There are four main dynamic effects:

• Compressors

• Limiters

• Expanders

• Gates

In the following table, I have listed their main features and applications.

Effect Description Comments

Compressor Allows you to reduce the

dynamic range

(difference in amplitude

between high and low

peaks) of an audio signal

Useful in situations where

the audio signal has a

very large dynamic range

Limiter Represents a drastic

version of a compressor

where the ratio is set

extremely high

Used mainly during

tracking in order to avoid

distortion and during

mastering to maximize

the overall volume of the

mix

Expander The exact opposite of a

compressor. It allows you

to increase the dynamic

range of an audio signal

Sometimes useful to “re-

generate” a track that

was over compressed

Gate An extreme application of

an expander where the

ratio is set extremely high

Very useful to reduce

unwanted noises during

“silent” passages of an

audio track

In the following figure you can see a diagram showing the effect that a compressor

has on a generic waveform. Notice how the gain parameter is set to boost the overall

level of the signal in order to bring back its highest peak to its original value.

Look at the following figure to see how a noise gate would alter a generic

waveform.

2. Delay Effects:

A delay effect is similar to an echo, in that the sound is repeated (after a brief time

delay) one or more times after the original sound. If the time between the original

signal and the repeated (delayed) signal is sufficiently small, it will not sound like a

distinct echo, but rather as a simple reverberation effect to represent spaces that you

are inside.

Delay effects are related to “propagation”. So, if you want to give the listener the

sense that a particular audio was recorded in a large room or a small room you would

turn to a delay effect to give that. The three dimensionality of an audio track has a large

to do with the delay effects.

This effect uses a RAM buffer to store the audio for a certain amount of time, after

which it outputs this audio. The RAM buffer will not always be just large enough to

store the amount of audio set by the current delay time, but will actually be

considerably larger sometimes, because many delay effects allow for their delay

parameter to be automated.

There are five main delay effects:

• Reverbs

• Delays

• Phasers

• Flangers

• Choruses

A Reverb simulates the component of sound that results from reflections from

surrounding walls or objects. It is in effect a room simulator.

A Phaser (also known as a phase shifter) is an audio signal processing technique

used to filter a signal by creating a series of peaks and troughs in the frequency

spectrum. The position of the peaks and troughs is typically modulated so that they

vary over time, creating a sweeping effect.

A Flanger is an audio effect produced by mixing two identical audio signals

together, with one signal delayed by a small and gradually changing period, usually

smaller than 20 milliseconds (kept below the threshold of echo perception). This

produces a swept comb filter effect: peaks and notches are produced in the resultant

frequency spectrum, related to each other in a linear harmonic series.

A Chorus is a delay for which the delay time is modulated by a Low-Frequency-

Oscillator (LFO). The most used LFO waveforms are sine and triangle. The effect can

produce interesting sounds, one of which is to produce the illusion of more than one

instance of the instrument/vocalist being present. What you get out of this effect

largely depends on your desire to experiment.

3. Filter Effects:

A filter effect is a frequency dependent amplifier circuit, working in the audio

frequency range, 0 Hz to beyond 20 kHz. Many types of filters exist for applications

including graphic equalizers, synthesizers, sound effects, CD players and virtual reality

systems. In its most basic form, an audio filter is designed to amplify, pass or attenuate

(negative amplification) some frequency ranges. Filter effects control the “timbre” of

the sound.

Common types include:

• Low-pass filter: passes through frequencies below its cutoff frequencies, and

progressively attenuates frequencies above the cutoff frequency.

• High-pass filter: passes high frequencies above the cutoff frequency,

progressively attenuating frequencies below the cutoff frequency.

• Band-pass filter: passes frequencies between its two cutoff frequencies,

while attenuating those outside the range.

• Band-reject filter: attenuates frequencies between its two cutoff frequencies,

while passing those outside the 'reject' range.

• All-pass filter: passes all frequencies, but affects the phase of any given

sinusoidal component according to its frequency.

I hope you enjoyed the lesson as much as I enjoyed making it. If you have any

questions do not hesitate to discuss with me so we can learn together! Thank you for

critiquing. Also, if you want to know more about my music, please visit my YouTube

channel. J

https://www.youtube.com/user/FrenzyPhrenesis

Regards, Take Care and Happy Learning!

*Word count: 998