Bellmetal is an alloy of Copper and Tin. It is a variety of Bronze(copper-tin alloy) with 78%-22% copper-tin combination. It is used for making bells as the particular combination gives strength and not easily giving for abrasions. This combination gives a particular 'clang' sound clear and distinct and reverberating, so it is used for bells.
The other variety of bronze is the white bell metal which has still more percentage of Tin in it. Vessels made of bell metal (or 'Vengalam' or Vellodu in Malayalam) were and still to some extent commonly used for cooking items like Payasam(Kheer) or boiling milk in temples and other big social functions in Kerala. They are less corrosive and less prone to abrasions in comparison to brass and copper vessels. While brass vessels and copper vessel become corroded and get the 'verdigris', bell metal or white bell metal vessels are not prone to catch verdigris*. They are commonly used in temples and homes for puja purposes and also cooking, and for making Ayurvedic medicines which need long time heating and boiling.
*(verdigris is the dark green or bluish green colour formation on the surface of brass and copper vessels exposed to air and humidity.)
As knowledge about metal and alloys are known to humans, even bell metal is produced in other countries, and in many places in our own country. However craftsmanship, unique methods of making and polishing etc make each one famous in its own way. For example in Kerala places like Nadavarambu, Mannar etc are more known as there are certain traditional families who have the expertise coming from many generations.
Bronze/bell metal is used for making cannons due to the strength and less corrosiveness it offers.
Variation in combinations, different shape, thickness or hollow all can affect the sound coming from a metallic product.