Technical foundations of TANDEM-STRAIGHT, a speech analysis, modification and synthesis framework

This article presents comprehensive technical information about STRAIGHT and TANDEM-STRAIGHT, a widely used speech modification tool and its successor. They share the same concept: the periodic excitation found in voiced sounds is an efficient mechanism for transmitting underlying smooth time–frequency representation. The tools are also based on the perceptual equivalence of two sets of independent Gaussian random signals. This equivalence makes it possible to discard input phase information intentionally and enables flexible manipulation of parameters.