Phase Quadrature

Phase quadrature occurs when two signals are +/- 90 degrees out of phase with each other. When signals are 90 degrees out of phase, only certain frequencies are cancelled, while two identical signals 180 degrees out of phase results in complete cancellation. Phase quadrature is sometimes used as an effect on devices such as phase shifters and choruses. For example, the UAD-1 version of the classic Boss CE-1 features a mode where the LFOs are 90 degrees out of phase to maximize the stereo spread.