A music ensemble system that enables changing the assignment of playing parts to performance terminals with a simpler operation. The music ensemble system comprising a plurality of performance terminals and a controller capable of communicating with the performance terminals to control playing of the performance terminals. Each of the performance terminals comprises a playing operation unit adapted to receive a player's playing operation and generates operation information, a terminal communication unit adapted to communicate with the controller to transmit the operation information to the controller, and a tone generator adapted to produce musical sounds based on sound instruction data received by the terminal communication unit. The controller comprises a controller communication unit adapted to communicate with each of the performance terminals, a music data storage unit adapted to contain music data including a plurality of playing parts, a playing control unit adapted to, upon reception of the operation information by the controller communication unit from the performance terminal, read out a playing part assigned to the performance terminal from the music data storage unit based on part assignment information indicating the assignment of the playing parts to the performance terminals, and transmit sound instruction data for sounding the playing part to the performance terminal via the controller communication unit, an operation unit having a part change operator, and a playing part changing unit adapted to modify the part assignment information according to a predetermined change pattern upon operating of the part change operator.