A gong is a percussion sonorous or musical instrument of Chinese origin and manufacture, made in the form of a broad thin disk with a deep rim, that has spread to Southeast Asia – a type of flat bell.
Gongs vary in diameter from about 20 to 40 inches, and they are made of bronze containing a maximum of 22 parts of tin to 78 of copper; but in many cases the proportion of tin is considerably less. Such an alloy, when cast and allowed to cool slowly, is excessively brittle, but it can be tempered and annealed in a peculiar manner. If suddenly cooled from a cherry-red heat, the alloy becomes so soft that it can be hammered and worked on the lathe, and afterwards it may be hardened by re-heating and cooling it slowly. In these properties it will be observed, the alloy behaves in a manner exactly opposite to steel, and the Chinese avail themselves of the known peculiarities for preparing the thin sheets of which gongs are made. They cool their castings of bronze in water, and after hammering out the alloy in the soft state, harden the finished gongs by heating them to a cherry-red and allowing them to cool slowly. These properties of the alloy long remained a secret, said to have been first discovered in Europe by Jean Pierre Joseph d’Arcet at the beginning of the 19th century.
The gong is beaten with a round, hard, leather-covered pad, fitted on a short stick or handle. It emits a peculiarly sonorous sound, its complex vibrations bursting into a wave-like succession of tones, sometimes shrill, sometimes deep. In China and Japan it is used in religious ceremonies, state processions, marriages and other festivals; and it is said that the Chinese can modify its tone variously by particular ways of striking the disk.
Gongs are broadly of three types. Suspended gongs are more or less flat, circular discs of metal suspended vertically by means of a cord passed through holes near to the top rim. Bossed or nipple gongs have a raised centre boss and are often suspended and played horizontally. Bowl gongs are bowl-shaped, and rest on cushions and belong more to bells than gongs.
Gongs produce two distinct types of sound. A gong with a substantially flat surface vibrates in multiple modes, giving a "crash" rather than a tuned note. This category of gong is sometimes called a tam-tam to distinguish it from the bossed gongs that give a tuned note. In Indonesian gamelan ensembles, some bossed gongs are deliberately made to generate in addition a beat note in the range from about 1 to 5 Hz. The use of the term "gong" for both these types of instrument is common.
