Guitar overdrive circuit based on CD4069 cmos IC. This digital logic IC contains 6 identical inverters composed of a complementary pair of mosfets. In this circuit they are used as analog amplifiers. Overdriving yelds a "warm" tube-like overdrive distortion sound. CD4013 is a dual D-register or flip-flop cmos IC. Here it is wired as bi-stable flip-flop and output Q is half the frequency of clock input. In music, one half frequency is equivalent to one octave below. Balance potentiometer sets the ratio between overdrive and sub-octave signals. Keep in mind that 4013 is a digital IC and will only understand a monophonic audio wave. Its output is a square wave with no envelope.