Van Evers used to sell an exoctic hardwood tuning kit, blocks of wood 3/4" X 1" X 1 1/2". Each type of wood resonates at a different frequency range. Very effective and does fine tune the sounds. I have tried over a dozen different type of hardwoods and have success with many, Ebony, Zebrawood, Bloodwood, etc. If you would like to try and can not get your hands on different hardwoods, write me.