This circuit is built around CMOS IC CD4011 and popular melody generator IC UM66. When touch plates are bridged by hand for a moment. the circuit starts to generate music. After a few seconds the music automatically stops.
Maximum supply voltage for this circuit is +5 volts. The IC UM66 can not operate beyond 3.3V voltage. IC 7805 regulator based power supply can be used to power this circuit.
Time delay can be changed by changing values of capacitor C1 and resistor R2. Three silicon diodes connected in series between pin 2 of UM66 IC and positive 5-volt rail keep voltage applied to pin2 of UM66 below 3.2 volts because of the drop of approximately 1.8 volts across them.