As used in electronic music, this refers to a lowpass filter whose cutoff frequency is set outside the audio range, so that all audio-frequency signals pass through.Such a circuit is used for a side effect: its property of shifting the phase of the output signal at an angle which is proportional to the input frequency, and to how far the cutoff frequency is from the audio band. When recombined with the original signal, this produces a paired peak and notch in the response curve, whose position in the spectrum can be varied by moving the cutoff frequency. The core of any phase shifter consists of one or more allpass filter circuits.

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