Korg Poly800/EX800 Users

I am looking for some help from some of you electronics engineer types that i know are on this forum.

I want to create a new detune circuit to include in the AtomaHawk kit.

The current detune is awful in my opinion. Korg made it that way because it was very cheap.

What I want to do is create a detune so that we can create really good phasing and a truly independent DCO2. The current detune is not actually independent clocking.

Can anyone suggest a way that I could produce a slightly offset oscillation based on a master clock source? And that slight offset could be adjusted using digital or analog signal voltage technique?

Mike