Imagine a concert where, instead of just listening to the music, you can participate in making it. Open Symphony is an interactive system that allows audience members to collaborate with the performers in creating the score. For example, as musicians in a string quartet play, the audience members can watch a graphical display representing the performers and their playing modes. The audience can then vote for various musical modes that the performers can then play. The system is easy enough for even untrained audience members to use.