A versatile speech analysis, modification and resynthesis system TANDEM-STRAIGHT and voice morphing based on it are introduced in relation to classical ideas starting from VOCODER in 1939. Interactive graphical user interfaces for direct manipulation of parameters and morphing parameters are also introduced to provide hints for readers to find make use of the procedures. Also an application of morphing procedure for detecting a high level auditory after effects in gender perception are introduced to highlight a prospective strategy for using morphing as a microscope in perceptual research.
