If your piano is sounding less then satisfactory there is a good chance the hammers have worn deep grooves in them. These worn grooves lead to a flattening out of the hammer which produces a harsh or unpleasant tone. In some instances it may lead to the opposite, a dull and muffled tone. In either case the solution may be to have the hammers filed down and voiced. This removes the deep grooves in the hammer and restores the hammer to it’s original pear shape. Here is a picture of the process. If you notice your hammers looking like this there is a good chance they need to be carded. Piano maintenance outside of tuning should be performed every 5 to 7 years depending on the use of the piano. Keep this in mind if you wish to keep your investment in tip top shape and if you wish to enjoy the tone of your piano all the time.