How did ancient Chinese people classify musical instruments?

Ancient Chinese people classified musical instruments using a system known as the eight sounds (ba yin). Rather than grouping instruments by how they produce sound, this system categorized them based on the primary material used in their construction.1

The eight categories are:

• Stone: Includes instruments such as stone chimes.1
• Earth (pottery): Includes instruments like vessel flutes.1
• Bamboo: Includes various tubular flutes.1
• Metal: Includes zhong bronze bells and bronze drums.1
• Skin: Includes drums.1
• Silk: Includes stringed instruments, which traditionally used twisted silk strings rather than gut or metal.1
• Wood: Includes percussive clappers and the yu, a tiger-shaped instrument.1
• Gourd: Reserved for instruments like the sheng mouth organ, which features bamboo pipes set into a gourd wind chest.1

This classification system was primarily used to organize the diverse array of instruments played in imperial orchestras.1