I have a problem: I have recorded and saved a song on my Casio Privia PX350 and I want to transfer this to a USB. I have tried to follow the manual: formatting the thumb drive, then selecting audio record, but I cannot get song record to light up to play the song as instructed. I was told to hold down the function key and select song record to choose the song you want to transfer. My unit will not allow me to do this. What am I doing wrong??