There is provided a musical tone control system which is capable of preventing control not intended by the user even when the user stops moving when controlling the generation of musical tones reflecting motion or physical posture of the user. A motion detecting device capable of being carried by an operator generates a detected motion signal corresponding to motion of the operator carrying the device, and transmits same to an external device. A musical tone generating device generates musical tones. A control device receives the detected motion signal transmitted from the motion detecting device and controls generation of musical tones from the musical tone generating device based on the received detected motion signal. The control device determines whether the operator is in a moving state based on the received detected motion signal, and when determining that the operator is not in the moving state, performs control to stop the generation of musical tones from the musical tone generating device after a predetermined time period elapses after the determination is made.