Flanging

How a short delay and feedback sweep a comb of notches, heard as a jet passing overhead.

Related

Comb FilteringModulationElectric guitar

The question

Flanging sounds like a band of tone sweeping through the midrange with a jet-like whistle. It comes from a very short delay, not from reverb or chorus.

How it works

The input is summed with a copy delayed by 0.5 to 10 ms, creating comb filtering. Notch spacing equals the reciprocal of the delay time. An LFO moves the delay slowly, so the notches sweep. Feedback deepens and sharpens them; some circuits sweep the channels in opposite directions for width. Past about 20 ms with low feedback, the effect leans toward chorus.

Settings and what you hear

A rate of 0.1 to 2 Hz suits a slow sweep across a section. Depth sets its range, and feedback above 60 percent whistles. An equal blend makes the comb clearest. On drums, cymbals take on a metallic sweep first; on sustained chords the motion is smoother.

What to listen for

Play the closed hats of a funk loop, engage the flanger and hear whether each tail is pulled into a moving metallic band. Push feedback from 20 to 70 percent and listen to the notches sharpen. Then check in mono, because an inverted stereo setting can thin the centre.

Common misconceptions

That flanging and chorus are the same effect; that more feedback is always better; that a flanged bus needs no mono check.

Sources

• Udo Zölzer, DAFX — Digital Audio Effects, modulation chapter — background checked, not quoted
• Curtis Roads, The Computer Music Tutorial, delay and comb filtering sections — background checked, not quoted

Used for fact-checking only; all prose is original.