Claude Debussy (1862-1918) fundamentally reshaped how composers approached harmony, orchestration, and the expressive possibilities of the piano. His music moved away from rigid harmonic rules toward suggestion and atmosphere, letting sound itself become the subject rather than merely the vehicle for melody. Debussy's innovations influenced generations of composers and remain central to piano repertoire because they demand that performers listen to color, balance, and the subtle decay of sound in ways that earlier music did not.