I haven't done this myself, but I guess you add the MIDI files the way you did when you used a floppy, press SONG and tab to floppy, and add your MIDI file. The keyboard behaves as if this were a floppy disk. I know there are people here that have done this, and hopefulle they will chime in and explain this better for you than I can do, since I don't have an emulator.