Interaction design of DMIs is not a simple task because it involves many relations between the musician, the DMI, other musicians and the audience. The interaction quality must be a central objective on a DMI design process. Using concepts from the field of HCI and affordance theory, we propose a model that could illuminate the designing of interaction events on multi-touch DMIs. Musicians should interact with interfaces that can be controlled with interaction and processing frameworks, and as such it is important to think and design what happens in these stages and how they relate to mapping and sound synthesis. Therefore, we must ensure DMIs use frameworks that allow users to control the synthesis process for specific tasks, such as musical performing or mixing, in an appropriate way in accordance with their desires.