This paper presents a jazz session system in which each player is independent and can interplay with all other players. In most previous systems, computer players only reacted to human player's performance with a fixed leader-follower relationship. Our system enables computer players to listen to other computer players' performances as well as human's performance and to interact with each other. Moreover, all players can communicate not only by listening to other players' performances but also by seeing each others' bodies and gestures. In our current implementation, the system deals with a jazz piano trio consisting of a human pianist, a computer bassist, and a computer drummer. These computer players have been implemented as separate processes on several distributed workstations. 1 Introduction It is important in jazz that all players improvise together while reacting to other players' performances with no leader-follower relationship. This is called interplay, and all playe..