The aim of this extended abstract is to introduce a grid created with the software Observer XT10.5 (Noldus©) to observe and analyze the state of Flow (Csikzsentmihalyi [6]) in 4 and 8 year old children when they interact with a musical machine for children music improvisation: the MIROR Impro. The MIROR Impro is one of the three components of the MIROR platform, that is an innovative adaptive system for music learning and teaching based on the “reflexive interaction” paradigm [1][3][4][10]. The theory of Flow has been used to explain the ability of the IRMS (Interactive Reflexive Music Systems) to imitate the music style of the user and their ability to enhance and maintain the attention of the user [11]. The results would support the hypothesis that the IRMS and the reflexive interaction may generate an experience of well-being and creativity. The Flow grid worked in an effective way and it was possible to indicate some aspects of the MIROR Impro to be improved. The research is carried out in the framework of the EU-ICT Project MIROR (Musical Interaction Relying On Reflexion).