Guitar Effects: Flange
Flange is an effect that is produced by two identical signals with one of the signals slightly delayed by a time that slightly, and continually changes.
Flangers are guitar effects pedals or units that mimic and elaborate upon a process used by sound engineers when recording. A sound signal would be recorded to tape onto two different tape machines at the same time. The recorded result of both machines would be rerecorded, or bounced, to a third tape machine. Slight differences in tape playback time from the two different machines, and from an engineer purposely slowing the tape down by holding or slowing the flange of the tape reel while being recorded to the third machine would create the effect that would eventually be named flange.
As electronic technology progressed, this effect was produced easier with solid state electronics in effects pedals. Flanger effects were popular in the psychedelic sound of the 1960's.