An interface which includes a MIDI send terminal having first and second pins for providing an output signal, an RS 232 terminal having first and second pins for receiving a signal from the MIDI send terminal, apparatus for coupling any MIDI output signal to the RS 232 terminal, the apparatus for coupling including apparatus for shifting a base level at which the signals are presented at the MIDI terminal to a base level at which the signals are received at the RS 232 terminal, apparatus for shifting the voltage swing of signals presented at the MIDI terminal to a voltage swing at which the signals are received at the RS 232 terminal, and apparatus for disabling the RS 232 terminal if a device to which the RS 232 terminal is connected would normally respond in an undesirable manner to unexpected data received on the RS 232 terminal.