Maestro filter mods ( frequency pot )

[reeko81]

Hi to anyone!
I falled in love with this vintage pedal, and I'm looking forward to building it.
I've recently understood too that Xotic robotalk pedal is a truly maestro filter inspired pedal, but they also added some cool option such as the frequency pot.
Has anyone Idea how to obtain on this maestro filter clone this useful control?
With this added pot and all other controls that tonepad clone has this would be the perfect envelope filter...

I'm still learning how to select a noise transistor, but please has anyone idea how could it be modded this maestro filter clone to obtain the same frequency control as on the Xotic robotalk?

Have a good DIYING!

[reeko81]

Nothing to say???