Among the great pianists of the 20th century, Aloys Kontarsky was one of the most versatile. He was an outstanding interpreter of new music - he regarded the title "Advocate of the Avant-Garde" as an honor, and the works of Stockhausen, Zimmermann, Kagel, and numerous other contemporary composers are inextricably linked to his name. Many pieces were specifically written for him and dedicated to him. Together with his brother Alfons, he formed an internationally leading piano duo for nearly three decades. "The brothers are genius," had already noted Eduard Erdmann enthusiastically when they were still studying with him. The precision and tonal homogeneity of their playing together were singular: "one pianist in two bodies," wrote an enthusiastic American reviewer. The contributions of the Kontarsky brothers to the repertoire for two pianos and for piano four hands are hard to overestimate. Through them, it gained stage readiness, and they are credited with the fact that this ensemble experienced a new flourishing around the mid-20th century. As a soloist of rarely performed works such as Reger's piano concerto and as a chamber musician, Aloys Kontarsky achieved extraordinary things, and not least, he was a sought-after and influential teacher as a lecturer at the Darmstadt Summer Courses for New Music and as a professor in Cologne. The pianist Jochen Köhler, one of Kontarsky's last master students, paints a highly vivid, multifaceted picture of his teacher. Biographical details are complemented by extensive explanations of Kontarsky's pedagogical work and his position in new music, as well as a comprehensive appreciation of his artistic legacy. In his own texts and a series of interviews, Aloys Kontarsky himself speaks, providing insightful glimpses into his work and thinking.