Chorus Effect - what is it and how does it work

With effects such as chorus, flanging, phasing and vibrato pitch modulation is used along with delay. With chorus, , an equal mix of the wet and dry signal is used with the wet signal being delayed and pitch modulated. The pitch is modulated using an LFO as the source and both the depth and rate are used to create varying ‘colours’ or textures of the effect.

The modulation depth is defined as intensity which is the range between the maximum and minimum values.

The rate determines the speed at which these maximum to minimum shifts occur. Too much depth when using chorus can sound as if the output is detuned whereas too little depth can make it sound less and less pronounced. Rate can have a dramatic effect on the chorus as slow rates create a more undulating and smoother effect whereas fast rates will create a speeded up wobble effect.

The relationship between rate and depth is very important and it is about finding a good balance between the two when processing sounds. The modulator shape is also critical as the shape denotes the periodic (unless chosen otherwise) cycling of the modulation destination. A sine wave shape will give a smoother cyclic effect, and is the most common LFO shape for chorus and flanging, as opposed to a square or pulse waveform which will have an extremely distinct effect as it cyclically switches between two delay times.
Whereas flanging will take the output and feed it back into the input (feedback) chorus does not adopt this process creating a far more subtle shimmering effect.

Chorus is often used on guitars, basses (mainly acoustic) and keyboard sounds like electric pianos and so on. Although chorus can thicken and widen a sound it can also push it into the background, so you need to be wary of the rate and depth of modulation particularly when using it for these purposes as opposed to using it for a specific colour.

Stereo chorus is even more interesting and dynamic and works by inverting the polarity of the delayed signal and combining it with the dry signal in one channel whilst keeping the polarity the same for the delayed and dry signals in the other channel. The result is interesting in that one channel will have frequency peaks whereas the other channel will have frequency dips.

One of the most important effects in the industry and rightly so. Let me explain what a chorus is, how to create it and how to use it.