What it is:

“A device used with an amplified musical instrument to give the impression that more than one instrument is being played.”

A Chorus is a modulation effect. In most cases, it produces a fuller, richer, thicker sound. Depending on the kind of chorus effect, it can also produce a wider stereo field. Chorus effects can be used to turn simple sounds into evolving synthetic soundscapes or add depth and character to instruments such as guitar, piano, electric piano and strings. It can be used on just about any sound, acoustic or synthesized. The main theory behind a Chorus is it is meant to mimic the variation in multiple parts played together, as in a Choir, or a “chorus” of voices, thusly creating the illusion or effect of more than one instrument being played at the same time.

A diagram of the Chorus effect process.

How it Works: A Chorus works by modulating delay times in milliseconds using a Low Frequency Oscillator(See picture above). A signal is sent into the Chorus effect, then it is split, sent through the delay, then mixed with the original signal before going through the output. The Low Frequency Oscillator is what makes the Chorus a Modulation Effect. The LFO modulates the delay time on the processed signal, resulting in a very slight change in pitch due to the change in speed of the LFO. This, combined with the delay, causes even mono inputs into the Chorus to have a wider stereo image coming out of the output. Although common Chorus effects use one delay, some Chorus effects can use multiple delays for an even more interesting sound. Stereo Chorus Effects implement an offset of phase on the LFO, and/or offset the delay thusly enhancing the Stereo Field of the signal.

Important Notes:

The Stereo widening effect produced by a Chorus is also heard in the common technique of Double Tracking, in which, two signals are played together, one with a slight delay.

A Chorus should not be confused with a Flanger, Phaser, or Unison effect, even though all three can have somewhat similar qualities, see other Soundphysics Basics posts for more information.

Choruses can cause phase discrepancies on a signal, so it is important in some cases to use the effect in moderation.

The Chorus Effect is commonly available as hardware, as well as software in Vst/Rtas/Aax/etc formatting, and is most often included in the box with any DAW.

Chorus Effects to look at:

(I am not being paid to sponsor any product below, and I have personally used every one of these)

http://valhalladsp.com/shop/delay/valhalla-uber-mod/

The Valhalla UberMod utilizes not only the principles of a Chorus effect, but takes it one step further, giving you such in-depth control over the effect as to produce a delay and echo effect, as well as a complex Reverb. All the Chorus you can handle, all in one plugin. MSRP: $50.00 US

http://www.uvi.net/en/software/thorus.html

An absolutely amazing Chorus effect that sounds incredibly clear and vibrant. The Thorus allows you to switch between a Stereo Chorus, or a classic Chorus, as well as control over the number of voices the effect produces. MSRP: $79.00 US

http://www.bluecataudio.com/Products/Product_Chorus/

This Blue Cat Audio Chorus is a freebie, but one that is certainly capable. It is a Chorus effect, no more no less, incredibly simple and easy to use, and perfect for beginners. This Chorus effect also utilizes a variable delay, making it an incredible Chorus all around, the sound quality is superb.

https://tal-software.com/products/tal-chorus-lx

A stupid simple Chorus that gets the job done, also, its free.