Simple Guitar Synthesizer Circuit

This circuit uses a CMOS Phase Locked Loop, the 4046, to produce a very unusual sound from a guitar, which sounds something like a synthesizer.
The signal from the guitar is amplified by two of the amplifiers in `the 4007. The amplified signal is used by the phase comparator to lock the VCO to the frequency of the mi note played. The VCO does not oscillate until a note is played, when using the low pass filter shown (i.e. the T5 k resistor and 100 n capacitor). lf the value of the resistor is increased, the VCO oscillates continuously at about 1 kHz (with no input signal). This gives very smooth note changes. The basic frequency may he changed by varying the 100 k resistor.