An electric musical instrument system comprising a musical sound transmitting means which transmits an audio signal emitted from a musical instrument and a musical sound receiving means which receives the audio signal, wherein the musical sound transmitting means and the musical sound receiving means both have a first mode and a second mode in which power consumption is lower than that in the first mode, the musical sound transmitting means comprises: a detecting means which detects rocking of the musical instrument; the electric musical instrument system being characterised in that the musical sound transmitting means further comprises: a transmitting means which transmits the audio signal to the musical sound receiving means in the first mode of the musical sound transmitting means and, when the detecting means detects rocking of the musical instrument, transmits detected information to the musical sound receiving means in the second mode of the musical sound transmitting means, and the musical sound receiving means comprises: a receiving means which receives the audio signal or the detected information; and a controlling means which processes the audio signal that has been received in the first mode of the musical sound receiving means and, when the detected information is received in the second mode of the musical sound receiving means, cancels the second mode of the musical sound receiving means and switches to the first mode of the musical sound receiving means. the musical sound transmitting means and the musical sound receiving means both have a first mode and a second mode in which power consumption is lower than that in the first mode, the musical sound transmitting means comprises: a detecting means which detects rocking of the musical instrument; the electric musical instrument system being characterised in that the musical sound transmitting means further comprises: a transmitting means which transmits the audio signal to the musical sound receiving means in the first mode of the musical sound transmitting means and, when the detecting means detects rocking of the musical instrument, transmits detected information to the musical sound receiving means in the second mode of the musical sound transmitting means, and the musical sound receiving means comprises: a receiving means which receives the audio signal or the detected information; and a controlling means which processes the audio signal that has been received in the first mode of the musical sound receiving means and, when the detected information is received in the second mode of the musical sound receiving means, cancels the second mode of the musical sound receiving means and switches to the first mode of the musical sound receiving means. a transmitting means which transmits the audio signal to the musical sound receiving means in the first mode of the musical sound transmitting means and, when the detecting means detects rocking of the musical instrument, transmits detected information to the musical sound receiving means in the second mode of the musical sound transmitting means, and the musical sound receiving means comprises: a receiving means which receives the audio signal or the detected information; and a controlling means which processes the audio signal that has been received in the first mode of the musical sound receiving means and, when the detected information is received in the second mode of the musical sound receiving means, cancels the second mode of the musical sound receiving means and switches to the first mode of the musical sound receiving means. a receiving means which receives the audio signal or the detected information; and a controlling means which processes the audio signal that has been received in the first mode of the musical sound receiving means and, when the detected information is received in the second mode of the musical sound receiving means, cancels the second mode of the musical sound receiving means and switches to the first mode of the musical sound receiving means.