Gong bells are bowl shaped and rest on cushions or hang from hooks. They are made mainly from bronze or brass but other alloys may be used. 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.