Abstract: A music on hold system is provided for key telephone systems having key stations, central office lines, and a muting relay for load resistance termination of the central office lines when they are on hold. A music source provides a music signal which is applied to the muting relay. When the telephone system controller receives a hold command from a key station, it generates a hold signal and applies the hold signal to the muting relay. In response to the hold signal, the muting relay applies the music signal to the central office line. Before being applied to the muting relay, the music signal is conditioned by passage through a gain control, a high frequency cut off filter, an amplifier, and a DC level shifter.