Chromatic harmony and modulation are powerful tools in music composition. They introduce notes outside the diatonic scale, creating tension and color. These techniques developed during the Romantic era, with composers like Chopin and Wagner expanding harmonic language and exploring distant key relationships. Key concepts include secondary dominants, augmented sixth chords, and pivot chords. These elements allow composers to create temporary tonicization, enhance voice leading, and smoothly transition between keys. Understanding these techniques opens up a world of expressive possibilities in music composition and analysis.