What was to be Bastide's magnum opus are accounts of the process of cultural reproduction among a group exposed to forced acculturation, the Afro-Brazilians, first brought as slaves to the colonial Northeast dominated by the sugar economy, and later participating in forms of mutual cultural inter-penetration in a pluralist society. This work led to three books that made Candomblé known to the world and that still make Bastide an important source for any work on theories of religions. His studies focused first on the African cults present in Bahia where many people kept dark skin colour, next in other locations of Northeast Brazil, and finally in the South, where the pigmentation generally got lighter.

Here too it matters to know the genesis of the scholarly endeavour. In the summer of 1943–1944, more precisely in January–February of 1944, Bastide did a study tour (or fieldwork session) in the area of Bahia and Recife. He had read up all that the Brazilian authors had written on the cults that the Bahian population (slaves and their descendants) had developed. He also came with a series of excellent contacts. But, once on the site, he cut some moorings, from books and from his academic environment, because experience conveyed to him some fresh meanings that were self-evident. Now he meets people, he sees and hears much, including carnaval.