Improvisio is a software for musicians who want to improvise visual music. Its development is part of the REACH project. It is useful to create visual improvisations in the frame of: audiovisual concerts, multidisciplinary projects, collaborations with visual artists or interactive audiovisual art installations. Improvisio interfaces with Somax2 and Djazz. In the context of musician-machine performances, the main functions of the program are: 1. to provide a visual representation of the musical elements in play in real time; 2. to enable improvised musico-graphic interactions between AI agents and musicians; 3. to make the operating processes of the artificial intelligence algorithm intelligible through the real-time visualization of musical and sound data. This article describes the first phases of development of the program. We want to show how the objectives of the REACH project, the results of the previous research, and the technical and aesthetic needs arising from the use of the first prototype in the framework of an art research project, lead to the proposal of an architecture and the implementation of the functions that are part of the program.