Book excerpt: At a time when the idea of a postracial society has entered public discourse, The Amalgamation Waltz investigates the practices that conjoined blackness and whiteness in the nineteenth and twentieth centuries. Scrutinizing widely diverse texts--archival, musical, visual, and theatrical--Tavia Nyong'o traces the genealogy of racial hybridity, analyzing how key events in the nineteenth century spawned a debate about interracialism that lives on today.