The art of making gongs was surrounded by great secrecy and mysticism. Making gongs required great skill and only certain families specialised in their manufacture, much like the making of samurai swords in Japan.
Tuned gongs also have a rim of varying depth, from the shallow rim as found on a tam-tam, to very deep rims sometimes greater in depth than the diameter of the gong itself. Some of the gongs found in the Javanese and Balinese Gamelan orchestras have this particular characteristic.
The characteristics of tuned gongs are a clear note with little or no shimmer, overtones or multitude of frequencies. The pitch may be tuned to either a Western scale (normally A = 442Hz) or an Eastern scale (e.g. a pentatonic scale). The tone can often be described as 'bell like'.
Examples of gongs tuned to the Western scale are the Tuned Gong range from Paiste (sadly no longer made at time of writing), plus certain models of the gongs made by UFIP in Italy.
Examples of tuned gongs from South-East Asia and the Far East include Thai, Burmese, Javanese and Vietnamese bossed gongs, Chinese Bao gongs, Gamelan gongs and Tibetan temple gongs.
The gong is then hammered by expert hammer strokes to produce the final tuning, before being re-heated and allowed to cool slowly to give it a measure of hardness. Finally, the gong is polished and decorated.
Modern Western gongs tend to be made from sheet metal, typically Nickel Silver, an alloy of copper, zinc and nickel. Some are also made from brass. The metal is specially made in rolling mills ensuring a closely packed and aligned metal crystal structure. The discs are then cut to size, heated and the edge folded over (where an edge exists). The face is then hammered from the rear to smooth out any large bumps and to 'tune' the gong. Once rested for 24 hours, a final tuning takes place and the gong is then decorated, cleaned and polished.