After few hours struggling with the keyboard, I have found best way to get the recorded file with the mid extension. We'll need a USB to do this operation. On the keyboard, tap the function button, then tap the 1 and 3 (< and >) to move to the media section. After that, tap the 6 button (Enter) and go to the Save section then tap Enter. After that choose the file which needed and tap Enter, rename the file then enter. It will display the "Sure?" text on the screen, just tap enter and wait. After that disconnect the USB and connect the USB to your computer, Go to the USB > MUSICDAT and your file will in there.