How did Franz Liszt’s late music anticipate composers such as Claude Debussy and Arnold Schoenberg?

Franz Liszt’s late compositions were highly innovative, effectively "flinging his spear far into the future" by challenging the musical conventions of his time. His work anticipated later developments in 20th-century music in several key ways:1

• Breakdown of Tonality: Liszt’s late development of chromatic harmony pushed the boundaries of traditional key structures. By using extensive chromaticism, he weakened the listener's sense of a home key, a process that eventually contributed to the total breakdown of tonality and the emergence of atonal music, as seen in the works of Arnold Schoenberg.12
• Impressionistic Elements: Liszt’s music contained passages that foreshadowed Impressionism, a style later defined by Claude Debussy. These elements included static harmony and a focus on instrumental "colours" that disrupted the forward motion of standard harmonic progressions.3
• Structural Innovation: By moving away from the rigid Classical sonata form and utilizing thematic transformation, Liszt influenced the move toward more integrated, unified musical structures. This approach to thematic development and the fusion of movements paved the way for the complex, expansive compositions of later composers.2