Atonality

"The forces that ultimately to lead to the breakdown of the tonal system, or at least the end of its dominance of Western music traditions, may be viewed as the logical extension of the direction in which music had been developing since the beginning of the nineteenth century.... We might also note that melody was gradually released from its traditional harmonic associations, with the result that melodic and harmonic successions began to exist in their own coloristic right." (Tonal Harmony with an Introduction to Twentieth-Century Music, Kostka and Payne, "Tonal Harmony in the Late Nineteenth Century.")