Matlab voice effects

Helo all engineers,

Im a newbie in audio processing. im doing project on voice effects on MATLAB. Most effects like delay, distort are very direct and easy. But i hav problems wth following effect

I want to change normal voice to chipmunks-like (high pitch) voice. What i can think of is to change higher pitch/frequency but it shortens the duration. I googled and some say phase vocoder can be use for frequency change and time stretching of signal. Is it possible and what does phase vocoder do???

Also, i want to convert male voice to females voice. I dont think changing pitch will do it. Because of different vocal tract between make and female makes the conversion hard. Can anyone give me some ideas?

Thank you