Though its name is a bit odd, a flanger produces a very cool guitar effect, so long as it's used in moderation. A flanger pedal can create a jet-sounding "whoosh" or oscillating metallic sound. Originally, the flanging effect was produced when a recording engineer would play back two identical signals and would slow down one of the signals by using his finger to vary the speed on the edge (or flange) of a tape reel. Since the original means of producing the sound was impractical, it became necessary to reproduce the effect in pedal form, with A/DA and Electro-Harmonix leading the way. Used tastefully, a flanger can add a cool, psychedelic vibe to a part (such as the intro to Heart's "Barracuda"). Overused, it can be enough to induce nausea.