Changing voice characteristics so it sounds like someone else voice
You may use the same pitch shift technique, but a little bit modified. If, classically, in pitch shift algorithm, each frequency component changes by multiplication of its frequency on some pitch-shift coefficient k, you may try:


Changing a little bit the amplitude of each spectral component.
Multiply each frequency component not by k, but k+v(f), where v(f) shows variation dependent on frequency f. Such variation must be of much smaller value than k. I mean k >> v(f).