tcStretch is allows time stretching, pitch shifting, and blurring.
Time stretch can be up to 1 million times slower. Pitch shift is plus or minus one octave. Blurring blends nearby spectral material to make the output less static.
Playing transients more slowly than non-transients emphasizes the stretchiness (good when playing in reverse mode with highly transient material). Adding blur brings in some subtle (or not so subtle) randomness which helps to keep the output less static.