[1] The computer algorithm allows frequency-domain modifications to a digital sound file (typically time expansion/compression and pitch shifting).
[2] This original phase vocoder did not take into account the vertical coherence between adjacent frequency bins, and therefore, time stretching with this system produced sound signals that were missing clarity.
The problem of the vertical coherence remained a major issue for the quality of time scaling operations until 1999 when Laroche and Dolson[4] proposed a means to preserve phase consistency across spectral bins.
It has been shown that by means of ensuring vertical phase consistency very high quality time scaling transformations can be obtained.
[7] Transfigured Wind by American composer Roger Reynolds uses the phase vocoder to perform time-stretching of flute sounds.