Obvious distortion is something that we would like to avoid, because most of the time we want to work with an accurate reproduction of a musical performance, but it has many creative uses in popular music, up to the point to be the distinctive feature that identifies some musical genres (Yes, I'm thinking about heavy metal, Black Sabbath, and all the crazy stuff that was created afterwards).
Audio Clipping
Commonly the distortion originates from the fact that we are using audio levels higher than the maximum expected by some of our gear. This can happen because we did not set the appropriate levels during recording or as a result of some gain stage in our pedal chain or our set of digital plugins in a DAW.
The effect of this is that the signal gets clipped at a certain point. Those hard clips comes with higher frequency components that may completely change the original sound timbre. Clipping is something that should be avoided during recording.
On the other hand, this hard clipping is actually used to design pedal effects like rock and metal guitar distortions. This is a popular effect/sound in rock music and it’s become widely-used in modern electronic music as well. The distorted signals tend to cut through a mix and bring warmth or grit to a tone.
Harmonic Distortion
Harmonic distortion is the introduction of extra harmonics that are musically related to the already present harmonics. This results in a change in timbre.
These extra harmonics are of two types:
- Even‑order harmonic distortion: These extra harmonics tend to sound musically sympathetic, smooth, and bright in a constructive way. For example, the tube amplifiers circuits.
- Odd‑order harmonic distortion: This one tends to sound rough and gritty, and is often associated with added richness and depth. E.g.: The distortion produced by an analogue tape.
Distortion, Overdrive, Fuzz
The terms "distortion", "overdrive" and "fuzz" are often used interchangeably, but they have subtle differences. Overdrive effects are the mildest of the three, producing warm overtones at quieter volumes and harsher distortion as gain is increased. A distortion effect produces approximately the same amount of distortion at any volume, and its sound alterations are much more pronounced and intense. On the other hand, a fuzz box alters the audio signal until it is nearly a square wave and adds complex overtones by way of a frequency multiplier.
Digital Distortion
We can also have digital distortion. And with this term we are not only talking about a DAW plugin or a digital peace of gear used to model analogue distortion. In the digital word but you can also experiment in crazier ways like playing with the word length or sample rate of an audio file. Reducing the word length creates quantization distortions, while reducing the sample rate can bring aliasing distortion.
Aliasing distortion has the interesting property that can generate frequencies below the fundamentals of the source sounds. That doesn't happen with most analogue distortion processes, which produce harmonic distortions above and based upon the fundamental frequency of the source.
Although digital distortion might not generally sound as musically pleasing as its analogue counterpart, it does have useful creative potential.
Conclusion
Distortion is an important concept, whether you are producing music that takes advantage of its features or you are fighting to reduce it, aiming to get completely clean sounds from a live performance.From my experience the only advice I can give is that if you want to have a classic distortion sound for your guitars or bass, always prefer the sound of analog amps/pedals over digital/modeling stuff. At post-production stage you can always give a try to your digital effects and compare the resulting sounds. The final choice will be up to you, but it is always a good thing to have some options, and not to be limited to the (probably not so good) available distortion plugins.
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Sources:
- http://www.soundonsound.com/sos/apr10/articles/distortion.htm
- http://en.wikipedia.org/wiki/Distortion_(music)
- http://www.electronics-tutorials.ws/amplifier/amp_4.html
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