Gongs are among the most powerful percussion instruments. There are two main types: 'bossed' (or nippled) gongs and 'flat' gongs. Bossed gongs have a raised center and produce a clear, definite pitch, often used in tuned ensembles like the Indonesian Gamelan. Flat gongs (like the Chinese Tam-tam) produce a wash of unpitched noise that builds in complexity as the metal vibrates—a sound known as 'shimmer' or 'bloom.' Traditionally, gongs were believed to have spiritual powers, used for signaling, warding off evil spirits, or healing. In Western orchestras, the tam-tam is used for dramatic climaxes and to create a sense of awe or dread.