Swallow mud. The name of the wall of the concert hall is swallow mud. Woolen curtains are often hung on the walls around the concert hall. At the same time, the walls are made into an uneven honeycomb shape, commonly known as swallow mud. The concert hall is a place for concerts and music-related activities. It is a place where people can feel the charm of music. It usually consists of a music hall and a small theater, with elegant decoration and appropriate layout.