Zu vier Händen – Interventionen für Konzertflügel is a piece that is rich in timbral and noise sonorities. It consists of numerous extended techniques produced by two players playing a grand piano – inside the piano with the hands, and by utilising different items, as well as at the keyboard. The sonic quality of the piece is shaped by a closely coordinated interaction between the players (at the keyboard and inside the piano). Many sounds are produced by the two instrumentalists through synchronised teamwork. In order to do so, the players are placed on opposite sides of the grand piano. By playing in this way, tones and noises are created one single player could not produce. Further explanation can be found in the Databank New Music (in German, see link below). The piece was revised once the development of a notation system for unconventional extended playing techniques had been finished. The revision was extensive, but was mainly concerned with the methods of notation, not the content of the piece.