Phaser (effect)

The Phaser is a delay time based effect for the music to the alienation of instruments ( usually guitar, but also keyboards and bass, rare drums) as well as the human voice is used as a sound effect. It is produced by a filter with a plurality of deletions and increases in the frequency spectrum, the frequencies of which are usually modulated so that the effect is changed periodically. The effect sounds similar to the flanger reaching certain phase shifts with a time- delayed copy of the original signal.


The effect is generated by the audio signal passes through two different signal paths. The signal part remains unchanged, while the other is sent through a series of all-pass filters. These filters shift the phases of all waves of any length, but not their amplitudes. The shifted signal is mixed with the original signal, with those waves cancel each other, the phase shifted by 180 °. That is, the more a wave trough a blended wave crest approaches, the more they will cancel each other out, and the quieter the respective frequency component. Shorter waves having a wavelength divided by an odd number will also be extinguished. This results in a comb filter structure; when using multiple -pass filters with different length shifts resulting in a complex comb filter structure.

By modulating the phase shift with a Low Frequency Oscillator typical phasing effect.


To set up the all-pass filter, it makes sense to use all-pass filters of second order, as these produce a phase shift of 0 ° to 360 °, so that, when added, a phase shift of 180 ° is given with the unfiltered signal at the cutoff frequency, resulting in a cancellation of this frequency to sequence has. In the phase shifts of 0 ° or 360 °, the sound is not changed.

About a weighting of the two signaling pathways can regulate the strength of the effect.

The Low Frequency Oscillator is used to dither the extinction frequencies periodically. It is two other parameters, the amplitude and frequency are controlled.


The American composer Steve Reich discovered the phasing effect in the mid- 1960s for his music. Some rock bands of the psychedelic era of the late 1960s used a phasing to give their songs a swinging and distant sound.

Sound Samples

  • Choir singing in the chorus of Sheer Heart Attack by Queen ( 1977)
  • E -Bass in Bring on the Night by The Police (1979 )
  • Electric guitar in Cockoo Cocoon of Genesis (1974 )
  • Electric guitar in Have a Cigar by Pink Floyd (1975 )
  • Electric guitar in Strange World by Iron Maiden (1980 )
  • Drums in Kashmir by Led Zeppelin ( 1975)
  • Some synthesizer on the album " Oxygène " by Jean Michel Jarre (1976 )