phase vocoder did not take into account the vertical coherence between adjacent frequency bins, and therefore, time stretching with this system did produce sound signals that were missing clarity. The optimal reconstruction of the sound signal from STFT after amplitude modifications has been proposed by Griffin and Lim in 1984. This algorithm does not consider the problem of producing a coherent STFT, but it does allow finding the sound signal that has an STFT that is as close as possible to the modified STFT even if the modified STFT is not coherent (does not represent any signal). The problem of the vertical coherence remained a major issue for the quality of time scaling operations until 1999 when Laroche and Dolson proposed a means to preserve phase consistency across spectral bins. The proposition of Laroche and Dolson has to be seen as a turning point in phase vocoder history. It has been shown that by means of ensuring vertical phase consistency very high quality time scaling transformations can be obtained. The algorithm proposed by Laroche did not allow preservation of vertical phase coherence for sound onsets (note onsets). A solution for this problem has been proposed by Roebel. An example of software implementation of phase vocoder based signal transformation using means similar to those described here to achieve high quality signal transformation is Ircam's SuperVP. Use in music British composer Trevor Wishart used phase vocoder analyses and transformations of a human voice as the basis for his composition Vox 5 (part of his larger Vox Cycle). Transfigured Wind by American composer Roger Reynolds uses the phase vocoder to perform time-stretching of flute sounds. The music of JoAnn Kuchera-Morin makes some of the earliest and most extensive use of phase vocoder transformations, such as in Dreampaths (1989). See also Audio time stretching and pitch scaling Vocoder References External links The Phase Vocoder: A Tutorial - A good description of the phase vocoder New Phase-Vocoder Techniques for Pitch-Shifting, Harmonizing and Other Exotic Effects A new Approach to Transient Processing in the Phase Vocoder Phase Vocoder - Phase vocoder description with figures and equations Signal processing Speech synthesis