Swapping multivibrator one shot circuit for cleaner switching any ideas??

[Haynesarama]

Hi people's

I'm hoping somebody could help me.
I'm playing around with a stereo switching device
Where the initial signal is fed into an envelope follower
With envelope followers output feeding into a cd4017 one shot circuit
Then into an ne570 to switch the outputs.

It's working as it should however the one shot circuits switching Isn't
Too accurate and I'm wanting to be able to change the sweep of the switching
With a pot, like a depth pot on a tremolo.
So to go from staggering between outputs or flowing between the outputs.

Has anybody got any ideas of how this can be achieved.

Here's the schematic I'm working from although it's been modified to have two inputs switching between the two outputs.

http://moosapotamus.net/IDEAS/stompboxology/Vol13No4/Page_12.gif

Thanks
Michael