Casio CZ/ VZ/ FZ - Pro Series

You may need to press both buttons simultaneously a few times to get it to rest 
to A=442Hz (the default on all CZs).

What you really need to do is bend a paper clip and push in the reset button 
on the underside on the synth. Do this with the power on. When you've 
pressed it, all the LEDs on the front panel will flash until you "un" press it.