Dan the Piano Man

That did the trick ! Thanks for the quick response and the easy solution.

I just recently acquired a Casio PX-560M. The start up tone is not Grand Piano, it's some kind of weird electronic voice. When I hit the GRAND PIANO button, nothing happens. I have to go into the Mixer within System Settings to select Grand Piano (or another tone). Thereafter the Keyboard operates normally including being able to go to GRAND PIANO instantly by selecting the GRAND PIANO button. Also from time to time (not very often) the keyboard will, on it's own, revert to the original start-up Tone in the middle of playing a song when I have not touched anything. I have to stop and go back into the Mixer to reset to the Tone I was using before the arbitrary and unwanted Tone change. I also purchased a 2nd PX-560 (for a second location) and do not have this issue with the 2nd keyboard. Any suggestions on how to repair ?