This is an effect that is achieved by splitting the audio signal, sending a dry version to the mixer, while sending the other part of the split to a variable phase-shift network and then on to the mixer where the dry and processed signals are mixed together.  
The result is a series of shifting phase cancellations in the form of frequency notches, peaks and dips. The sound is a characteristic "whooshing" and, like all effects, needs to be used with some subtlety if it is not to become too obvious. 

phasors (for guitar) are often comb filters rather than time delay effects. 

Phasing is similar to flanging 

  one to six
by Philip Glass
  one to six
with dynamic phasing 26 seconds