The Probert Encyclopaedia of Music

GONG

The gong is a Chinese musical instrument made of an alloy of copper (about seventy-eight parts) and tin (about twenty-two parts), in form like a round flat dish traditionally with a rim about six centimeters in depth. It is struck by a kind of drumstick, the head of which is covered with leather, and is used for the purposes of making loud sonorous signals, of marking time, and of adding to the clangour of martial instruments.
Research Gong