3 Madden, Timothy Smith, Ronald Bruce Wright, Matthew Wessel, David 2001 Preparation for Interactive Live Computer Performance in Collaboration with a Symphony Orchestra ICMC 2001 Habana, Cuba This paper describes the design, implementation, and use of an interactive computer-based instrument in the context of a composition for orchestra and live electronics. We will begin with an overview of the piece from a compositional point of view, emphasizing the musical goals for the electronics aspect. Then we will discuss the extremely demanding technical requirements of integrating live electronics with a full orchestra. We will describe the interactive instrument in detail, emphasizing the novel mapping of performer's gestures to computer-generated sound events and the novel OpenSound Control-based structure of the software.