As early as the Shang dynasty both north and south China had produced massive clapperless bells (nao), the predecessor to the kind of bells from Marquis Yi's tomb. Constructed with the mouth of the bell upward, the nao is arranged in groups of three for playing simple tunes. In later times the number of bells required for a performance increased, and though they remained similar to the nao in shape, they were suspended mouth-downward from a frame.