The steelpan, often called the steel drum, is the only major musical instrument invented in the 20th century. It originated in Trinidad and Tobago during the 1930s. When the colonial government banned skin drums and bamboo sticks (Tamboo Bamboo), local musicians began experimenting with metal objects, eventually settling on 55-gallon oil drums discarded by the petroleum industry. The top of the drum is hammered inward into a concave shape and then 'tuned' by creating distinct, flattened sections that vibrate at specific frequencies when struck with rubber-tipped mallets. The steelpan is a versatile instrument capable of playing complex chromatic melodies, and it has become the national instrument of Trinidad and Tobago. Large steelbands can consist of up to 100 players, performing everything from calypso and soca to classical arrangements of Bach and Beethoven.