In recent years, several musical systems have been developed, which can perform cooperating with emotional information. For most of these systems, however, users are required ability to play the music well and knowledge. So we constructed a musical session system with which children and novices can play pleasantly. The session system is composed of two parts. One is musical part which is a kind of instrument with which users can perform the music by modifying the combination of some phrases. Another is visual part which can visualize a change of the condition of the performance on the real-time session. This prototype system was evaluated by many children. The result of evaluations showed that children could play this system pleasantly.
