Actually, since the keys are just plastic, i've always used rubbing alcohol. Cuts right through fingerprints and gunk and leaves no residue. I just use a cotton ball with rubbing alcohol on it and it will dry on its won fairly quickly or you can follow up immediately with a soft dry cloth.

If it helps, I used to work in a music store cleaning and maintaining over 200 pianos and organs, brand new grands included. Never any damage to any of them.


Jeff