Dave Smith Instruments SYNTHESIZERS

Hi guys,  There's something i don't really get.  Does anybody 
know why if you have an LFO modulating the Delay time of any of 
the delays it modulates the pitch in strange ways. I don't get the 
connection. Maybe I'm missing some basic law of synthesis or 
something.  Not that I can't use the effect but I'm just not 
undestanding why it happens.

Steve