Quintet.net is a real-time interactive environment for intermedial composition and performance on local networks as well as the Internet. Since its premiere in 2000, the environment has been used in several large projects connecting players in Europe and the U.S.A., a Munich biennale opera project among them. Quintet.net implements, in a virtual environment, the metaphor of five performers under the control of a conductor, thus dealing with important aspects of symbolic, aural and visual communication among the participants and the network audience. A composition development kit has been added to the environment (which consists of Client, Server, Listener, Conductor and Viewer) to facilitate the development of pieces that take full advantage of the wide continuum between composition and improvisation.