Yamaha UX256 Owner's Manual page 22

Installing the Driver
9. Make sure that
"OMS MIDI Device Setup" dialog. Check all Ports 1-16 check boxes.
10. Click
[OK]
11. The system displays a dialog box that enables you to save the setup file.
Enter the file name and click
22
"USB-MIDI 1"
.
and multiple Port numbers are listed in the
.
[Save]