Adventures In Audio

Learn how to use chorussing (works in all DAWs)

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The chorus effect takes a signal, delays it slightly, then modulates the delay time up and down. This modulated signal is mixed with the original to create movement and interest in a sound.

Here I'll use the Air Music Technology Chorus plug-in (AAX/AU/VST), which is simple to use and very effective.

I'll use a simple 220 Hz sine wave and an electroacoustic guitar to examine the effects of the controls, and I'll take the settings to their extreme values to examine the range of sound textures that are possible, many of which would not be useful musically but could be used for special effects.

Automated transcript

The chorus effect takes the signal delays it slightly then modulates the delay time up and down this modulated signal is mixed with the original to create movement and interest in a sound here i'll use the air music tech chorus plugin which is simple to use and very effective in this exploration i'll use a simple 220hz sine wave and an electro acoustic guitar to examine the effects of the controls and i'll take the settings to their extreme values to examine the range of sound textures that are possible many of which would not be useful musically but could be used for special effects as chorus is often best used as a stereo effect i'll use a file that has the same sine wave signal on both channels as the source in this demonstration i'll use a vectorscope as a visual aid to be able to see the stereo effect of the chorus as well as hear it here's the sine wave with the chorus plugin bypassed notice that in the vectorscope the trace is a vertical straight line this shows that the signal being the same on both channels is mono muting the right channel so that the signal is only on the left does this muting the left channel so that the signal is only on the right does this the upper quadrant of the vectorscope between l and r and the mirror image lower quadrant represent signals that are mono or stereo if the trace extends to the plus s or minus s quadrants then it contains information that is out of phase if the trace is a horizontal line between plus s and minus s then it is completely out of phase

let's start with the controls at their default settings which clearly air music tech believes to be a generally useful starting point with the exception that i'll set the depth to zero so that there is no delay and therefore no chorus effect i'll then gradually raise the depth from zero to maximum then return to a setting that would commonly be useful the calibration of depth in milliseconds by the way refers to the maximum delay time

uh

what we can notice is that at first the tips of the vectorscope trace stay within the boundaries of left and right but at a certain point they stray into the outer phase quadrants let's see that again

mm-hmm

here is the point where the tips of the trace just touch the edges of the stereo zone which in this example for a 220 hertz sine wave is a depth a maximum delay of 0.81

milliseconds

this is interesting and also of relevance because audio that contains out of phase information can cause problems for mono compatibility and is something that a wise engineer will always check to continue i'll reset the depth to its default starting point next i'll sweep the rate control through its range of settings

clearly there's a range of rates that would potentially be musically useful and higher rates might be useful for special effects particularly science fiction sound effects it's worth bearing in mind that it is widely considered that vibrato in singing should have a rate around 6 hertz this doesn't mean that you have to set the chorus rate to 6 hertz which in this example is too high to sound musical but it's always worth having a reference point in mind when making artistic decisions to continue i'll set the controls back to their defaults pre-delay is an overall delay that is applied to the modulated signal again i'll sweep the control through its range of settings

this has less of an effect on a sine wave signal than a real world music signal so i'll apply it to a recording of electro acoustic guitar which is a good source for demonstrating any type of time modulation effect

as you can hear if you listen closely the sound gets richer with longer pre-delay times and there is probably a point at which the degree of richness is optimum this will vary according to the instrument or vocal that you're chorusing lfo low frequency oscillator lr phase represents the relative phase of the modulating signal in the left and right channels if the phase is set to zero then both channels are in step and the result is mono the overall level modulates but there's no stereo image shift if the phase is set to plus 180 degrees or minus 180 degrees then when the left channel is at for instance three milliseconds of delay the right channel is advanced with respect to the input signal by the same amount three milliseconds this will create a stereo image that swings widely between left and

right

the default setting in this plugin is plus 90 degrees which sounds subjectively the same as minus 90 degrees the 90 degree relationship sometimes known as quadrature places the modulating signals in the left and right channels one quarter of a wavelength out of step which seems to be a good starting point for chorusing although all options should be explored

lfo waveform offers the choice of sine or triangle wave there's a very subtle difference between the two the triangle wave other than going back and forth has a constant rate of change the rate of change of the sine wave varies throughout its cycle the sine wave therefore sounds more swirly than the triangle both in the subjective texture of the sound and in the pan of the signal i'll demonstrate this using both the sine wave and electro acoustic guitar

the feedback control will work on the sine wave but other than for science fiction effects which i'll come to later does not provide a useful demonstration so the electro acoustic guitar in this case is better source material the feedback control works very much in combination with pre-delay so i'll step through a range of combinations of settings some of which will work musically better than others so

finally the mix control normally in any plug-in the mix controls the amount of effects you want to hear but in the case of chorus it can dramatically change the sound texture here's a sweep of the mix control on electro acoustic guitar with otherwise default settings

it's pretty much an amount control but here it is with a high level of feedback

so

as mentioned earlier this chorus plugin is capable of a useful range of sci-fi oriented sound effects here are a few

so

effects can get weirder when the controls are in motion here are a few demonstrations

do

so

uh

in summary the chorus effect can be both musically useful and capable of creating interesting sound textures these demonstrations have only scratched the surface of the possibilities i'm david mellor course director of audio masterclass thank you for listening.

Thursday March 10, 2022

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David Mellor

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Adventures In Audio.

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