This is the square that portable stereo I use the microphone to speak when the stereo play the music is gone.

Is the stereo connected to a computer? Should be the computer is set to microphone priority, the microphone a sound, background music will become very small or no, just like the radio station hosts speak music will be much smaller, the human voice stops the music will return to normal volume. Turn microphone priority off.

If it is just a simple audio use, not connected to the computer is also so, then the audio itself is this is this design, can not be changed.