From Fonitronik's description of the VCO:

Late in 2009, Thomas Henry asked me if I wanted to do a beta test of his new approach to a CMOS 4046 based VCO. He and Scott Stites already had done some work on this project and I had the privilege to be the 1st “user” to build and try it.

As soon as I built it on breadboard I was stunned by the features, especially the hard sync: blew me away… Scott Stites did an awesome job on testing and to document the circuit, and you will find all the information necessary to set up and calibrate this VCO at his site: Birth Of A Synth (Scott Stites)

This design uses the 4046 in a new way. It is certainly not the “perfect” VCO as you would call the CEM3340 a perfect VCO, nevertheless, it is an awesome VCO with a lot of character, while the tracking/scale is quite good. Thomas was able to get a very decent 8 octaves out of it