What is the "bang" in many Japanese classic songs?

This is a wooden fish. Of course, wooden bangzi will be used in some places. Judging from your lyrics, it is more like a wooden fish.

Wooden fish, percussion instruments. It was originally an accompaniment instrument of Buddhism "Brahma Blow" (a religious song). Wang Ming folded the "Three Things Zhi Tu": "Wooden fish, carved in the shape of fish, is empty in it, and the sound of knocking is loud ... Today, the praise of Buddhism is used by the Vatican." Popular among the people since the Qing Dynasty. Muyu Muyu is a wooden product, and its appearance is similar to the shape of a fish head. China appeared very early, but its recorded history is relatively late. This special object is not only seen in temples. As early as the Ming and Qing Dynasties, wooden fish had been used in court music, Kunqu opera and folk music. Usually, the big wooden fish is made of Sang Mu or Ailanthus altissima, with a maximum surface diameter of more than 40 cm and a relatively low sound. Small wooden fish are generally made of sandalwood or mahogany, with high pronunciation. There are two kinds of wooden fish used in temples: one is round and the other is long. Generally speaking, round wooden fish have various specifications, and long wooden fish are mostly about one meter.