In this chapter, the use by twentieth-century composers of tone color, or timbre is explained with examples by those who made its use central to their compositional output. Poland, freed from the bonds of communism and the Soviet state, relaxed controls over the arts and in 1956 initiated the Warsaw Autumn festival where avant-garde Polish and Western music could be heard. Kazimierz Serocki cofounded the festival, contributing to the percussion canon his timbre-based sextet, Continuum. In the United States, the American composer George Crumb definitely had an ear for timbre coupled with a love for percussion evident in the works discussed. A young Polish/American composer, Marta Ptaszynska, created a number of works for both solo and ensemble percussion in the latter half of the century. Her work Siderals was conceived as an audio-visual, or mixed-media work utilizing ten percussionists, magnetic tape playback, and lighting. The three composers highlighted in this chapter approached the use of timbre in differing ways.