Your piano has a unique voice, just like a person. A brand new piano tends to have a rich even tone across all the ranges. Over time inconsistencies crop up and cause some notes to be brighter, louder, more brassy than others. Voicing is a process of manipulation of the hammer felt, and alignment of the hammer to the strings to bring your piano back to it's factory original voice. This type of work cannot be completed unless the piano has been recently tuned and regulated.