phaser

A phaser is a modulation effect that shifts the phase of the input signal and mixes it back with the dry signal¹. It works by splitting the signal and sending one path through a series of all-pass filters, called stages, whose position is moved by an LFO, creating ever-changing phase inconsistencies between the two signals². This produces a cyclical, swirly, swooshing sound³. Notches occur between stages and cancel out audio, with roughly one notch every two stages, so more stages mean more notches and a more intense effect⁴. One of the earliest guitar effects, it was originally developed to recreate the sound of rotating organ speakers⁵.