What is the sound effect on Law and Order theme?

The sound effect used on the Law & Order theme is a distinctive "chung chung" sound. It is created using a waterphone, which is a musical instrument that consists of a metal tube that is filled with water and has metal rods suspended inside it. When the rods are struck with a mallet, they vibrate and create a resonating sound that is similar to the "chung chung" sound on Law & Order.