④Built-in Music Switching & Volume+/- Button(a) To switch musics: Short press this button to play the built-in music, short press again to play next piece. NOTE: If you need to pause the music, please press [] on the remote control. If you want to turn off the music, please turn the Product off.(b) To adjust volumn: Long press this button to adjust volumn from low → high→ low again in cycle. (When the volumn reaches maximum/minimum, there will be a notification tone ).