Close relatives of delay effects, modulation effects change the pitch and time of a delayed signal using a Low Frequency Oscillator, or LFO. Two of the most common modulation effects are chorus and flange.

Created by mixing two identical signals together and delaying one of the signals by a constantly varying time, the flanger is perhaps the simplest of modulation effects. The resulting effect creates a kind of whooshing sound as the delay signal rises and falls in varying parts of the frequency spectrum.

Similar to a flanger, a chorus effect is created by mixing the source signal with one or more pitch-shifted copies of it. Each copy is then modulated by an LFO. A chorus is different from a flanger in several ways. First, the time between the modulated delay signal and the original source signal is longer in a chorus than it is in a flanger. Also, a flanger only has one delayed signal, whereas a chorus may have two or more. And finally, choruses do not feed any of the processed signal back into the processor.

Common Chorus and Flanger Parameters

Below are some of the most common parameters for the flanger and chorus effects:

• Rate. Sets the frequency of the LFO modulating the delayed signal.
• Width. Shifts the phase of the LFO modulating the delayed signal.
• Shape. Sets the type of waveform the LFO will use to modulate the delayed signal.
• Delay Offset. This is the time (in milliseconds) between the source signal and the delayed signal.
• Delay Modulation Amplitude. Sets the speed of the LFO modulating the delayed signal.
• Delay Feedback. Variable feedback, or regeneration, produces multiple decaying repeats. Increasing the feedback value increases the number of echoes, as well as the resonance that is created as one echo disappears into another.