DIY samplers

[Christopher List]

Hi folks - 

I was wondering if anyone could point me in the right direction for some good 
books that would touch on the subject of sampler design. I'm really curious 
about how samplers control the pitch (playback rate, I know). Does the 
processor just send out clock messages at different rates - i.e., is it a 
matter of the firmware "waiting" between clocks, or is there usually some kind 
of dedicated hardware that the processor can just tell what playback speed to 
use? 

- Thanks,
Chris