Timbre is among the most important and the most elusive aspects of music. Visceral and immediate in its sonic properties, yet also considered sublime and ineffable, timbre finds itself caught up in metaphors: tone color, wet acoustics, or in Schoenberg's words, the illusory stuff of our dreams. This multi-disciplinary approach to timbre assesses the acoustic, corporeal, performative, and aesthetic dimensions of tone color in Western music practice and philosophy. It develops a new theorization of timbre and its crucial role in the epistemology of musical materialism through a vital materialist aesthetics in which conventional binaries and dualisms are superseded by a vibrant continuum. As the aesthetic and epistemological questions foregrounded by timbre are not restricted to isolated periods in music history or individual genres, but have pervaded Western musical aesthetics since early Modernity, the book discusses musical examples taken from both classical and popular music. These range, in classical music, from the Middle Ages through the Baroque, the belcanto opera and electronic music to saturated music; and, in popular music, from indie through soul and ballad to dark industrial.