How did Richard Wagner and Franz Liszt contribute to more chromatic harmony?

Richard Wagner and Franz Liszt were pivotal in expanding the use of chromaticism to heighten emotional expression and eventually destabilize traditional diatonic harmony.

Richard Wagner

Wagner’s contribution centered on developing a continuously chromatic harmonic vocabulary, most notably in his music drama Tristan und Isolde. He utilized a wide variety of techniques—including altered chords, chains of secondary dominants, and resolutions to unstable chords—to blur functional tonality. By frequently postponing or evading the cadences that traditionally defined harmonic direction, Wagner used unresolved harmonies to mirror dramatic themes like unrequited passion. His work effectively initiated the gradual dissolution of the diatonic system that had governed Western music since the 18th century.12

Franz Liszt

Liszt employed chromaticism as a powerful tool for characterization and coloristic effect. In works such as Les Préludes and his Symphony to Dante’s Divina Commedia, he used chromatic and "writhing" melodic lines to depict intense emotional states, supernatural forces, and the struggle of the soul. By integrating these dissonant, chromatic elements into his symphonic writing, Liszt helped move music toward greater freedom from Classical formal constraints.13