IMP Homework Podcast Episode Three Transcript


Hello, I'm Wes Perdue from the East Bay area of San Francisco, California.

Welcome to the third episode of my podcast series that fulfills my weekly homework assignment for the online course from Coursera titled Introduction to Music Production.

This week we will be looking at a fairly specific feature of the digital audio workstation: the available options for insert effects in the channel strip.

Definitions for all key terms can be found in the show notes at

One major component of a DAW is its mixer, which is composed of various channels that are each controlled by channel strips that manipulate the sound flowing through that channel. The insert section is a part of that, and it's where we can add custom effects. These effects can be included with the DAW's software package, or can be third-party effects built according to a plug-in standard supported by the DAW.

There are three major categories of plug-in insert effects: dynamic effects, delay effects, and filter effects.

Dynamic effects control the amplitude–that is, the volume–of a sound.

Delay effects control the appearance of propagation of a sound by manipulating when a sound is heard relative to other sounds. This can be done by manipulating a sound's phase, or by delaying a sound.

Filter effects affect a sound's timbre by manipulating the frequency spectrum it is composed of.

Dynamic Effects

I'll cover dynamic effects first. Dynamic effects control the volume of a sound, and work in the amplitude domain of sound.

Examples of dynamic effects include the compressor, limiter, expander, and noise gate.

A compressor reduces the dynamic range of an audio signal; that is, it narrows the difference between the quietest and loudest sounds.

An expander expands the dynamic range of an audio signal; that is, it does the opposite of a compressor and increases the difference between the quietest and loudest sounds.

A limiter enforces an upper limit on the dynamic range of an audio signal by reducing or clipping the amplitude of any sound that goes over the threshold. They are commonly used at the end of a channel strip or master track to avoid harsh clipping.

A noise gate reduces to zero the amplitude of sounds below a specified threshold. They are commonly used to remove low-level noise from quiet parts of a recording. Gates can be used for other things too, like ducking one sound when another is heard.

Delay effects

Delay effects control the timing of sound, and work in the propagation domain of sound. They manipulate when a sound is heard relative to another sound by manipulating a sound's phase, or by delaying a sound. Our hearing is able to detect this difference in delay or phase shift between each ear, and our brains interpret these differences spatially. This is how we are able to determine distance and direction of sound relative to our location.

Examples of delay effects include reverb, delay, and chorus. Phasing and flanging, both special effects, are also in the domain of delay effects.

Reverb simulates a space, like a small room or a large cathedral. It does this by calculating sound reflections using a model of a room or an algorithm, and then playing back those manipulated, delayed reflections.

Delay simulates an echo. It's similar to reverb, but the time between a sound and its echo are typically longer, for example, like the difference between a large room and a canyon.

Chorus simulates multiple voices from one voice. When a choir sings, its members do not start and stop at exactly the same time; that's how your brain knows there are multiple singers, even if they're signing exactly the same thing. That's how a chorus works.

Phasers and flangers are special effects that don't quite model real-world effects, but they are in the delay domain, because they manipulate the timing and phase of sound. Definitions are in the show notes.

Filter effects

Filter effects control the timbre of an audio signal by manipulating its frequency spectrum. They work in the frequency domain of sound.

Examples of filter effects include high pass, low pass, band pass, and notch filters, and equalizers.

A high pass filter cuts frequencies below a specified cutoff frequency, and a low pass filter cuts frequencies above specified cutoff frequency.

A band pass filter is a combination of a high and low pass filter, as it cuts frequencies outside a single narrow band at a specified frequency.

A notch filter is essentially the opposite of a band pass filter, as it cuts a single narrow band around a specified frequency.

An equalizer is a more sophisticated example of filter effect, as it is usually composed of more than one filter. An equalizer raises or lowers levels of frequencies at a number of bands on an audio signal.

A parametric equalizer is the more common type of equalizer in audio production, as it is a more flexible type of equalizer. It has a variable bandwidth of effect for each band, often referred to as the Q parameter. As well, the shape of the filter at each band is often configurable, with shelf or cut filters usually available at the outer bands.

A graphic equalizer is most commonly seen on consumer devices, and is a simpler type of equalizer. The bandwidth of the filters are not adjustable, and the shape of the filter on each band is not configurable.


This is just an introduction to the types of effects available in each of the three categories of plugin insert effects.

Plugins available in each category are numerous and vary widely. There are also plugins that combine features of each of the types to create new categories, like distortion effects, glitch effects, or amplifier or speaker cabinet simulations.

We will be looking at each of the types as the class continues: dynamic effects will be covered this week, and delay and filters will be covered next week.

I hope you've enjoyed this introduction. If you'd like to submit feedback for this podcast, please use the contact form at Thank you for listening.