This dissertation uses multi-sited ethnography to explore how the technological manipulation of sound in live jazz performance conditions the meanings, feelings, and politics of racial difference. Situated primarily in two multi-room jazz venues, Jazz at Lincoln Center (JALC) and the Montreux Jazz Festival, I analyze three years of participant observation with musicians, audio technicians, acousticians, and sound system designers. I analyze four main categories of technology: (1) physical acoustics; (2) sound isolation, (3) sound reinforcement (amplification); and (4) digital measurement, prediction, and manipulation technologies. My overarching goal is to provide new ways to understand live performance with more attention to the technologies, architectural designs, and human labor crucial to any sonic event. I show not only how the built physical spaces and technologies I observed are inscribed with human judgments about music and sound, but how the spaces themselves exhibit their own agentive force in conditioning social behavior. I thus rethink live performance as a dynamic network of materials, technologies, and human and nonhuman practices and meanings. My second intervention uses the figure of jazz—and, more specifically, the sound of jazz—to investigate how the intersection of technology and sound exposes new ways to think through questions of human difference. Focusing primarily on race, I show how ideals of scientific objectivity and “pure and clean” aesthetics challenge racial tropes of Black sound as “noisy” or disordered while complicating jazz’s political force as an agent of oppositional energy and Black cultural distinctiveness. Chapter one, “‘Some Rooms Make You Shout’: Physical Acoustics and the Sound of Jazz,” shows how the designers of JALC’s Rose Theater, a prestigious 1,300-seat concert hall, acoustically encoded musical and social values into the physical materials of the room and the building that surrounds it. Namely, I show how particular aspects of the hall’s physical acoustics reveal overlapping investments in western aesthetic values and Afro-diasporic priorities, including call and response, participatory interaction, and heterogenous timbral palettes. Chapter two, “‘Some Rooms Make You Whisper’: The Art of Isolation and the Racial Politics of Quiet,” focuses on Rose Theater’s acoustic isolation, accomplished through a rare and expensive “box-in-box” construction that physically disconnects the hall from any vibratory connection with the outside world. This unique architecture fosters an uncannily quiet, sequestered aural environment that counters a range of histories of racist white listening that associate Blackness, Black bodies, and Black spaces with various forms of “noisy” sonic excess. The hall’s extraordinary quietness also reinforces a culture of attentive listening that enmeshes the sound of jazz with western ontologies of aesthetic musical autonomy. Relatedly, chapter three, “‘Make Yourselves Invisible’: Transparency, Fidelity, and the Illusion of Natural Sound,” demonstrates how ideals of fidelity and transparency are embedded within electroacoustic sound systems, and how my interlocutors design and operate such systems to foster a “pure and clean” aural environment. I show how my interlocutors aspire to an illusion of a “natural,” technology-free sonic experience but deploy an array of technological systems to do it. My analysis challenges traditional notions of fidelity—and sonic mediation itself—by revealing musical experience as a constellation of vibrant interactions between acoustic vibrations, amplified sound energy, and physical human bodies. Chapter four, “Tuning the Room: On the ‘Arts’ and ‘Sciences’ of Sound and Space,” analyzes how my interlocutors design and calibrate sound systems using state-of-the-art digital equipment to foster what they call a neutral, “colorless” sonic environment with “the same sound everywhere.” This process of “tuning the room” conjures novel ontologies of sound and space as objects of detached observation and technoscientific manipulation. In chapter five, “Black Boxes, Pink Noise, and White Listening: Rationalizing Race, Gender and Jazz,” I demonstrate how the objectification of sound and space is entangled with raced and gendered epistemologies of scientific knowledge production. I further analyze these approaches to sound and space for their underlying entanglements with what Lipsitz calls a “white spatial imaginary”: an ostensibly neutral environment conducive to discriminatory systems of capital accumulation. These and other entanglements complicate the oppositional, counter-hegemonic potential of jazz and other forms of Black performance.