An ensemble system enabling even performer unskilled in playing a musical instrument to easily grasp the difference in tempo from the performance of the facilitator. The circle corresponding to the performance terminal “Facilitator” is indicated fixedly on the center line of the vertical lines. The circle corresponding to the performance terminal (for example, piano (1)) of each user moves horizontally correspondingly to the difference from the performance terminal “Facilitator”. If the press of a key of performance terminal lags behind that of the performance terminal “Facilitator” by one bar, the circle moves left onto the vertical line next to the vertical center line. If the press of a key of the performance terminal lags behind that of the performance terminal “Facilitator” by half the bar (two beats), the circle moves left by half the interval between the vertical lines from the vertical center line. If the press of a key of the performance terminal leads that of the performance terminal “Facilitator”, the circle moves right (FIG. 7).