Open and closed form in interactive music

Performing music includes substantial listening skills on part of the performer. Performing with an interactive computer requires the performer to interact with the computer and intuitively and consciously include this information in the responsiveness of his playing. The interaction can be expanded to include the performer's high-level decisions typical of open-form notation. These decisions can be used for defining and re-defining the computer's role in the further development of the piece. In this paper I describe how such an open-form notation is used in the interactive man/machine performance environment of my composition 'GUITAR' for acoustic guitar and interactive computer. The performance environment functions as a perception-based multi-parameter space where the performer's score provides means for exploring the space. The open-form notation emphazises the interactive functionality of the space, and a performance becomes one of many possible explorations of the space.