Digital delay effect: avoiding clicks on delay time change I'm implementing a digital audio delay effect using a simple circular delay line. Changing the delay time by making the delay line longer or shorter introduces discontinuities in the audio signal, resulting in clicks.

What would be the best (most pleasing for the ears) strategy to avoid such clicks when changing delay time?
If you are not changing the delay length very often, and you don't want to have a Doppler effect that comes from continuously changing the delay length, then try a cross-fade. Both delay lengths should be running simultaneously for a moment, and you would fade the old one out while fading the new one in.