By Jeff Strong

Chorus takes the original sound and creates a copy that is slightly out of tune with the original. The chorus’s shifted pitch varies over time. This variance is called modulation, and the result is an effect that can add interest and variety to an instrument. Chorus is used extensively to add fullness to a sound, particularly guitars and vocals.

Most chorus effects give you several parameters with which to work, as the following list makes clear:

  • Rate: The rate dictates how fast the modulation happens. This parameter is described as a frequency (usually 0.1 to 10 Hz). The frequency actually doesn’t refer to a pitch; rather, it describes how many times per second (Hz) the oscillation happens. The oscillation is controlled by the depth parameter.

  • Depth: The depth parameter controls the amount of pitch modulation that’s produced by the chorus. The settings are often arbitrary (you can get a range of 1 to 100). This range relates to a percentage of the maximum depth to which the particular chorus can go, rather than an actual level.

  • Predelay: The predelay setting affects how far out of time the chorus’s sound is in relation to the original. This setting is listed in milliseconds, and the lower the number, the closer the chorused sound is to the original in time.

  • Feedback: The feedback control sends the affected sound from the chorus back in again. This allows you to extend the amount of chorusing that the effect creates. This setting can also be called stages in some systems.

  • Effect Level: This could also be called mix in some systems. The effect level controls how much effect is sent to the aux return bus. This allows you to adjust how affected the sound becomes.