"Your piano also may require periodic voicing. The process of voicing can adjust the relative brilliance of a piano and provide an even gradation of volume and tone over the entire range of the keyboard. Voicing procedures may involve reshaping the hammers, the use of needles on the hammer felt and/or the application of special softeners or hardeners in order to produce the best sound possible. You should discuss with your technician what changes in your piano's tone are practical and together, decide what steps should be taken to effect these changes.
Although you may have your piano tuned regularly, you must specifically request regulation or voicing procedures. These procedures aren't included in a normal tuning. It should also be noted that voicing can only be accomplished after a piano has been freshly tuned."(PTG,2005)