Bak (hangul: 박; hanja: 拍) is a wooden clapper used in Korean court and ritual music. The person playing the bak is called , serving as the conductor or musical supervisor for the group. The bak creates the clapping sound if clapped to indicate when the music starts. The upper part of the six long and narrow boards are tied with a string, and the lower part is held open with both hands, and then closed rapidly, creating a clear impact sound.