His work is full of invention and, most importantly, extreme unpredictability, and wide emotional range even within a single work, a style that may be categorized as "empfindsamer Stil". It is no less sincere in thought than polished and felicitous in phrase. His keyboard sonatas, for example, mark an important epoch in the history of musical form. Lucid in style, delicate and tender in expression, they are even more notable for the freedom and variety of their structural design; they break away altogether from both the Italian and the Viennese schools, moving instead toward the cyclical and improvisatory forms that would become common several generations later.