There are many children's toys. After being squeezed or pressed, there will be sound or music. What is the principle?

Yes, when making a toy, a chip containing a music integrated circuit is put into the toy. After the toy is put into the battery, the chip can be electrified, and it can be controlled to make sound through an external button. Some toys have many buttons that can make many different sounds, which is why music is programmed in the music chip in advance. Once the music is programmed and packaged, it cannot be modified.