A music session system which makes it possible to expand the functions of electronic musical apparatuses. The server is connected to a first electronic musical apparatus belonging to a first user and capable of executing music sessions, a first personal computer (PC) belonging to the first user and capable of executing additional functions, a second electronic musical apparatus belonging to a second user and capable of executing music sessions, and a second PC belonging to the second user and capable of executing additional functions via a network so as to perform transmission and reception of information to and from these apparatuses. When the first electronic musical apparatus requests the apparatuses belonging to the second user to execute a music session and an additional function, the first and second electronic musical apparatuses are instructed to execute the music session, and the first and second PCs are instructed to execute the additional function.