In King's Vibrato Maurice O. Wallace explores the sonic character of Martin Luther King Jr.'s voice and its power to move the world. Providing a cultural history and critical theory of the black modernist soundscapes that helped inform King's vocal timbre, Wallace shows how the qualities of King's voice depended on a mix of ecclesial architecture and acoustics, musical instrumentation and sound technology, audience and song. He examines the acoustical architectures of the African American churches where King spoke and the centrality of the pipe organ in these churches, offers a black feminist critique of the influence of gospel on King, and outlines how variations in natural environments and sound amplifications made each of King's three deliveries of the I Have a Dream speech unique. By mapping the vocal timbre of one of the most important figures of black hope and protest in American history, Wallace presents King as the embodiment of the sound of modern black thought.