Basic Sound Synthesis: Part 5 – Effects Part 2

Distortion: A popular effect when used on electric guitars, distortion is the process of boosting the synthesizers signal over the limit, to the point where it clips and can remove parts of the audio range. It is also possible to distort signals so that additional harmonics in the frequency range are created. Distortion, or ‘overdrive’, are not common effects used on synthesizers due to the unpleasant clipping of the signal, although used creatively it can produce interesting effects.

Phaser: In phasing, the signal is fed through an all-pass filter which creates peaks and notches (highs and lows within the frequency spectrum). When done statically, this creates modifications in the signal from the synthesizer, but to create a moving effect an LFO is used to sweep the comb filter, creating the standard phaser sound. Phasers can be used in various different stages, such as 2, 4, 6, 8, 16, or even more, with the more stages being used the more effective the signal.

Flanger: A variant of the artificial chorus and phaser technique, flanging was originally produced by slowing down identical reels of tape, which would produce a sweeping effect of the signals becoming out of sync with each other – but only by a very small amount. Likewise, in artificial flanging a delay technique is used to multiply the signal and constantly change the delay between the signals within milliseconds. This delay effect creates a jet plane-style sound which unlike phasing creates a comb filter effect with the harmonic bumps and dips of the signal being in series with each other. Like the chorus and phaser effects, flanging is modifiable by changing the rate of the sweeping delay, as well as the feedback and depth of the signal. When the feedback of the flanging signal is turned up too high however, it resonates to an unpleasant degree.

Delay: One of the most commonly used effects in sound synthesis; delay (or ‘echo’) is the relatively simple process of copying the original signal from the synthesizer and playing it several times between different time intervals. More exotic techniques can be used, such as reversing the delay playback, and creating feedback loops which run an infinite period of time.

Reverb: Originally created manually by plates and springs, reverb is one of the oldest effects in music in general, and is frequently used in sound synthesis. The effect is similar to creating sound in a large room, where the sound will reverberate due to the size of the room. The effect is created digitally by using many delays, and using accurate simulations of room sizes and their effects, which creates the fake effect of the sound hitting the listener’s ears first and loudest, followed by the reverberation effect afterwards.

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