Early 1995, Yamaha introduced a new range of synthesizers with interesting interface capabilities. For the first time, these machines were compatible with three standards: MIDI, Macintosh and PC. To support the PC interface, the MU5, MU10, MU80 synthesizers and the SU10 sampler came with an RS232 serial port, providing connectivity with the PC. This spurred the author into designing an RS232-to-MIDI converter that’s supported by a freeware driver from Yamaha.Initially, these sound generators were designed to work with what Yamaha called ‘HOST PORT’ supporting software. In fact, only a few sequencers were actually capable of directly supporting this functionality. Fortunately, Yamaha designed a driver that permits the use of a serial port as a standard MIDI interface to almost any sequencer running under Windows.An interesting spec of the Host Port mode of the MU5 is its ability to retransmit all messages arriving on the MIDI IN connector to the RS232 port. The same ability was available in the other direction, from RS232 to MIDI OUT. In industry-speak, this is called a ‘gateway’.