“Very famous during the 70’s and 80’s, the Flanger effect can be used on almost any audio track: on drums, voices synths or guitars, from a subtle effect to a deep alien-like voice effect, enjoy it!
Despite its simple user interface, Blue Cat’s Flanger is very versatile: harsh and metallic or smooth and soft filtering effects, it can do them all, for free!
The stereo version also lets you smoothly transform it into a stereo flanging effect with a single knob. Push the “Spread” slider and hear the difference: the effect is turning around your head, and the sound takes another dimension, spread into the stereo field.”
Source : Blue Cat Audio