Hands on: Make the most of modulation effects in your music

Previously we've taken an in-depth look at audio effects and how you can best use them in your music. We covered distortion, delay and reverb. Here we’re going to finish off by taking at look at modulation effects such as phasing, chorus, flanging and pitch vibrato, while also touching on pitch shifting.

Whereas distortion, delay and reverb have an obvious ‘in your face’ influence on your audio, modulation effects tend to sound more subtle. Nevertheless, they are key elements of many types of music, including reggae, trance and 1960s-style psychedelica.

However, because the controls on modulation effects are often labelled with obtuse terms such as frequency, depth and rate, they can be a bit tricky for novices to get their head around. But don’t worry because we’re going to explain how the effects create their distinctive sound, describe what the various controls do and give you some tips on how to make the most of them in your music.

One of the great things about modulation effects is that they are quite simple for today’s computers to create. This means the plug-ins that create these effects don’t take up much processing power, so generally you can get away with using as many of them as you like, even on slower computers.

Vibrato
Effects such as chorus, phasing and flanging are called modulation effects because they are created by using a process known as pitch modulation. To create this pitch modulation, a low frequency oscillator (LFO) is used. An LFO is like the oscillators used in synthesisers to create sound, except with an LFO the frequencies are so low that they can’t be heard by human ears.

However, an LFO is useful because it can be used to influence other elements of a sound. In the case of pitch modulation, the sound is first delayed by a few milliseconds and then the LFO is used to modulate this delay time.

The most basic type of pitch modulation effect is vibrato. That’s because it uses the LFO to modulate the frequency of the sound to create the familiar vibrato pitch wobble. Unlike other pitch modulation effects, vibrato only uses the modulated signal.

The controls on a vibrato plug-in are usually simple, with the rate dial controlling the speed of the vibrato and the depth setting governing the depth of the pitch modulation.

All the more complicated forms of modulation effects mix the modulated signal back into the original signal to create their distinctive sound. This is the reason people generally use the effect’s own wet/dry controls rather than trying to control the wet/dry mix via a send/return loop.

Flanging
Flanging is probably the most pronounced of the modulation effects, as its comb filtering-type sound leaves a strong impression on the resulting audio. Like all the effects in the modulation family, it first delays the audio signal by a few milliseconds and then modulates this delay time using an LFO. However, flanging also adds some of the processed sound back into the effects loop.

The feedback control is used to vary the amount of the processed sound that re-enters the loop and as you add more feedback, the comb filtering effect of the flanger increases dramatically.

Typical controls on a flanger include rate, feedback and delay. A flanger’s rate control sets the rate or speed of the flanger’s frequency sweep. The feedback dial dictates how much of the processed audio is fed back into the effects loop. The higher the setting, the more metallic sounding the effects will be. Finally, the delay control affects the frequency range of the flanger’s sweep by adjusting the initial delay time.

As flanging is a dramatic effect, you’ll usually want to use it sparingly. Use too much of it and the listener may become bored and irritated by the sound. However, it has been used quite liberally on some songs in the past, usually during the 1960s. The Beatles’ track Tomorrow Never Knows from Revolver was one of the first commercial songs to make use of it.

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