The purpose of this study is to explore the verbal communication that three 7-year-old children are engaged in when given the task of composing music together. The data consist of a video-observation of the activities that unfold when they try to manage a composition task using a keyboard and two novel technologies called "MirorImpro" and "MirorCompo," respectively. The questions posed by the children and their verbal dialogue are analysed. The results show that they pose few questions and that they do not use musical terms in their conversations. Instead, they come to invent a concept which is shown to fill several mediating functions for the children in the activities, such as facilitating discernment, playing/composing music and sharing their musical experience. The need for further analyses of young children's verbal communication in music activities is pointed out in order to get hold of children's perspective on music and in the development of a music education informed by sociocultural theory.