Change pitch small increments like 1 Hz at a time

Thanks for your Help...

is there a way to Change pitch in small increments like 1 Hz at a time ?

Or know of a program that can do this ?

Looks like what I need is a 'frequency shifter' for .mp3 like:

voice output from tts , to lower all frequencies by 8hz .

Or know of software that can do this ?

Thanks