Welcome to the PSR Tutorial Forum, Arska!
You can find the information you are looking for in the Tyros4 Owner's Manual on page 27 ("Memorizing Song/Style Paths").
- In the Song Selection display, navigate to the desired drive (e.g. HD1) and go into the desired folder.
- Press "VIEW" to bring up the List View display.
- Select any Song (MIDI) file here.
- Press "MEMORY" (display button "E") and then one if the SONG I - IV buttons.
- Press EXIT button to close the File Selection display and test the assigned SONG button.
Best regards,
Chris