The working of the circuit, Start from IC1 is installed as astable multivibrator to generate frequencies about 1 Hertz by R1 and C1 work together. Which generate the output frequency from IC1 is send through a R2-resistor to pin 5 of IC2. Which is a control voltage pin of IC1, will causes a tone that generate a oscillator at IC2 has pitched – bass sound as control voltage from output of IC1 there.