This dissertation maps out a new approach to studying small-scale societies and their place in global historical narratives by examining the history of coastal East Africa's immediate interior from the first millennium to the 1800s, in particular the Mijikenda-speaking societies that live adjacent to the Swahili port city of Mombasa, Kenya. Drawing insights from comparative historical linguistics, oral traditions, archaeology, and archival records, I demonstrate that while Mombasa has been a hub of Indian Ocean commercial activity for over a millennium, the communities that live only kilometers away have for just as long rejected the signifiers of Indian Ocean cosmopolitanism that pervade the urban center's social, economic, and religious life. Mijikenda speakers shrunk their settlements at the same moments that Mombasa urbanized; they were receptive to the ritual knowledge of outsiders but rejected Islam; and they pioneered long-distance inland trade routes that transformed East Africa's economy, but only participated selectively in maritime commerce. I argue that Mijikenda speakers' divergences from their Swahili neighbors helped to lay a foundation for commercial expansions across coastal East Africa and ultimately enabled the region to integrate into global networks. I conceptualize my approach to East Africa's Indian Ocean littoral as a history of what I term "global dissonance," which explores how disconnecting from certain social or economic networks is not an act of self-isolation, but generates new possibilities within other mosaics of interaction. Departing many global histories that focus primarily on integration, such as the literature on Swahili urban centers and Islamic maritime networks of the Indian Ocean world, focusing on dissonance illuminates new narratives, such as the transformations in social and economic life that occurred when global maritime networks went into decline in the mid-first and mid-second millennium CE. By foregrounding the actions of small-scale societies and places seldom visible in regional macro-narratives, this study identifies new processes through which the coast of East Africa became a part of the Indian Ocean world.