The sound produced by the voice playback chip is determined by the sound programmed into the chip. Then when it is applied to the circuit board, there are some buttons or the program writes the playback mode to trigger the playback of the sound.
The underlying program for reading/writing is written and burned into the programmable voice chip. Of course, the sound files can also be burned into it together. If the program supports it, you can also add an external memory to achieve the function of sound storage expansion.