Immersive audio is an upcoming innovation within the world of professional audio reinforcement. The amount of possibilities of enhancing the listening experience is enlarged drastically by setting up arrays of speakers in front of and around the audience. Technological advancements make it possible to render recorded audio channels for an immersive audio system during live performances. These advancements rely on spatial audio rendering techniques, which will be described partly in this thesis. The elaboration on these techniques serves to clarify how the created audio effects are generated. Object-based audio (OBA) mixing allows the rendering of (pre)recorded audio channels for an immersive audio system. OBA mixing allows to be very close to the listening experience. In the project that is presented in this thesis, an in-depth look is taken at the use cases of immersive audio in the application of live performances. The users of immersive audio systems, who carry the responsibility of developing and executing the content that is reproduced over such systems, are determined and involved in defining a number of common use cases. Through the ability of defining specific requirements, these use cases lay the foundation for the development of a concept of a mixing tool for immersive audio systems. These requirements are supported by a respective definition of quality. Qualitative research is also done in terms of generating ideas. Furthermore, a look is taken at existing relevant software, with analogous functionalities. The research is bundled in a concept for a mixing tool, which is worked out in a visual mock-up. This mock-up is used in an evaluation study, to create an insight into the desirability of the concept. The concept is also laid parallel to its requirements that have been set for it. At last, elements of the concept, which are missing despite their relevance, are discussed. Further research is suggested for the development of these elements. Additionally, some use cases that arose during the project for the use of OBA mixing in the further future are presented.