Chinese music has a long history dating back to the Shang Dynasty. During the Han Dynasty, the imperial court established a music department to collect and edit ancient melodies. Most Chinese folk songs use a repetitive formal structure. Confucius believed that music could be used to calm human passions. The development of Chinese music occurred in four periods: the Formative Period where music honored ancestors, the International Period with influences from trade, the National Period where music was enjoyed by all classes, and the World Music Period combining Western and traditional forms. Instruments include flutes, zithers, lutes, fiddles, gongs and wood blocks. Chinese music uses pentatonic and heptatonic scales as well as the lu and