Vianna, a Brazilian anthropologist and writer, looks at the "invention" of samba as Brazil's national rhythm. Romantics saw it as an art form that changed spontaneously from a repressed music of the marginal and impoverished to a national symbol after the abolition of slavery. For Vianna, however, the story is more complicated. Samba's rise to national status after the 1930s grew out of a long and complex negotiation between rich and poor, weak and powerful. When bossa nova emerged in the late 1950s, it was attacked as violating "true Brazilianness" -- which was seen to lie in samba de morro, or samba of the slums. Similar reactions erupted later against the influence of rock and electric guitars. But in truth, these old debates about "authenticity" and "innovation" are not confined to popular music in Brazil alone. Instead, they form an integral part of a heritage that marks all parts of the Americas, where Africans came as slaves and emerged from three centuries of slavery to remake (and in many cases take over) the definition of national musical expression. Samba has, after all, become one of Brazil's great gifts to the world.