Automatic player pianos and internet form a music performance system for a music session on the automatic player pianos through data communication between the automatic player pianos, and a communication time lag and mechanical time lag are unavoidably introduced between the data transmission and the data reception and between the data reception and tone generation; one of or both of the time lags are compensated by employment of an electronic tone generation, presumption of key positions or presumption of key event so that the slave automatic player piano generates the tones almost concurrently with the tones generated through the master automatic player piano.