Complex sentence: His advances in musical language, such as extreme chromaticism and quickly shifting tonal centres, greatly influenced the development of classical music; his "Tristan und Isolde" is sometimes described as marking the start of modern music.
Split into simpler sentences: His advances in musical language, such as extreme chromaticism and quickly shifting tonal centres, greatly influenced the development of classical music. His "Tristan und Isolde" is sometimes described as marking the start of modern music.