Introduction to music Production 6 – Distortion
Distortion is caused by overloading an input signal to the point in which it clips (peaks), resulting in grit, fuzz, noise, and other timbral (tonal quality) changes. Depending on the audio processor, soft or hard clipping may occur.
This is called harmonic distortion because it adds (or amplifies) harmonics at multiples to the original tone because of the distorted waveform change.
See the image below for a visual reference of what is happening to waves as they are clipped in both manners.
Image source: Guitar Gear
As you can see, the waveform is altered because it is being limited in some way from the audio system. This doesn’t necessarily mean the input signal is bad, but if you are trying to avoid distortion, you’ll need to turn down the input.
Unlike harmonic distortion, speaker distortion is due to the diaphragm of the speaker reaching the limits of it’s excursion (speakers move back and forth)
For a deeper, mathematical analysis, check out this article from Gizmodo
A few types of distortion are frequently used in musical applications, both for live performance and studio production.
We’ve already discussed harmonic distortion – overloading an input signal, but also very common are saturation, bit crushing, and overdrive.
Saturation effects originated from the amount of magnetism a tape could hold. The tape’s oxide particles could cause distortion when more magnetism was added, creating a warm ‘tape saturation.‘ Saturation plugins typically try to model tape saturation, and usually can handle a wide range of possibilities for a sound.
Here’s a plain sine wave and then a saturated sine wave.
Overdrive is an effect usually modeled after overdriving tube amplifiers to the point of distorting. Most overdrive pedals and software effects will have a ‘gain stage‘ to prevent further fuzz due to an overloaded output signal from the effect. Most guitar distortion/fuzz pedals are in the style of overdrives.
Here’s a plain sine wave and then an overdriven sine wave.
Bit Crushing (Bit Reducing) does not follow the previous examples that create harmonic distortion. The concept of bit crushing is to lower the bit depth of a sound to create artifacts (distortion – usually clicks and pops – caused by errors in processing higher fidelity audio to lower fidelity audio). 16, 24, and 32 bits are common depths for modern music, but bit crushing can reduce those to 1 bit. It is found more commonly in electronic music, and is a more destructive audio process.
Here’s a plain sine wave and then a bit crushed sine wave. The bit crusher settings are maxed out to show the drastic amount of difference it can make.