Taking Bently's idea a step further...Start with a light colored wood like maple, cut kerfs lengthwise and glue a dark colored strips into the kerfs and then slice them off the end. You can make an octave at a time and draw, burn or simply use a knife to mark the white keys. as I did here with guide lines. You will need to size them for whatever width blade you have. The only problem is that you will get bat wings at the top of the kerfs.
Edit to add: you could fill the kerf with a dyed epoxy instead of wood.
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.
