In the design process of interactive sound walk art installation, the composer must think his sound design in a real or a virtual space according to the listener?s promenade. For a given piece, the sound designer leaves to the interactor a certain amount of freedom and to the system, according to its level of self-sufficiency, a certain amount of autonomy. This paper presents an analysis of this fundamental composition choice between determinism, emergence and interactivity. In the first part, this problem is stated as the position of an art piece in the D.I.S. (Designer/Interactor/System) triangle. We analyze from this point of view several interactive pieces. The second part concerns mainly the design process of The Listening Walker scripted versions. This interactive sound walk relies on the technology and the design principle of video games. In the scripting style, the designer takes the point of view of the interactor, who becomes the narrator. We conclude by an introduction to the second version of the same piece written according to the emergent style. In this case the designer takes the point of view of Non Player Characters controlled by the system.