Voice controlled electronic music toy circuit

Circuit working principle: The piezoelectric ceramic piece HTD converts the sound into an electrical signal.
After being amplified by the direct-coupled amplifier composed of VT1 and VT2, C2 is coupled to the base of VT3,
causing it to conduct and trigger the music integrated circuit 9300. The music signal is passed through VT4 Amplify and drive the speaker to produce
sound. At the same time, part of the audio signal enters the base of the switching circuit VT5 through R7 , causing
it to be turned on and then sent to the multivibrator composed of VT6 and VT2.