pitch shifting, the college try:
http://web.mit.edu/aalamb/ww.../lab3.html

I've done pitch shifting with bucket-brigade delay lines (analog),
and ring buffers (a2d, microprocessor, d2a).
The effect worked well despite the flaws in the method (I did not attempt to detect pauses in speech).

You simply read data into an array of 256 at one rate, and read it out at a faster rate. When you hit the end of the buffer, move the pointer to the beginning.