Updated: Jun 17
When you depress the keys on your piano's keyboard, hammers strike the strings, causing them to vibrate in a certain way that produces sound waves. The specific condition of your piano's hammers - their age, shape, density, and surfaces - all figure prominently in the tone produced by your piano's strings.
Piano hammers are made of layers of high-quality wool felt wrapped tightly and glued and (usually) stapled to a wooden core. New hammers have a symmetrically round shape, smooth surfaces, and plenty of resilience - they are "springy" and have the ability to quickly bounce back into shape after briefly being compressed by their collision with the piano's strings.
A warm, resonant piano tune is the result of symmetrically rounded, smooth, and resilient hammers striking the strings. Each hammer strikes the strings at a precise point - the "crown" of the hammer, which is the highest point of the symmetrically round hammer shape.
With age and with use, the wool felt undergoes at least three changes as a result of repeated collisions with the steel or copper-wound strings. First, the surface of the felt develops string grooves. Second, the overall shape of the hammer transitions from rounded to somewhat flattened on top. Third, the wool felt loses its resilience and becomes compacted and dense. All three of these changes - string grooving, flattening, and compaction - tend to deteriorate the quality of the sound produced by the interaction of the hammers with the strings.
The grooving and flattening of the hammers results in the condition that, instead of one precise point on the hammer striking the string, instead there is a line-shaped segment of the hammer that hits the string. The deeper the grooves, and the flatter the hammers, the longer this line-shaped segment is. The compaction of the wool felt reduces the resilience of the felt, reducing the ability of the hammer to swiftly bounce away from the string after hitting it.
The grooving, flattening, and compaction tend to make the piano's tone somewhat harsh, tinny, and brittle.
If you are not happy with the tone of your piano, I'd be glad to stop by and let you know if a hammer voicing procedure would likely improve the quality of the tone. I generally remove the action (hammers and wippens) and take it to my house to file the hammers, removing small amounts of wool felt from the sides with sandpaper, to nearly eliminate the grooving and to return the hammer to its original rounded shape. I then use tools with sharp needles to carefully penetrate the compacted wool felt and help to return it to its fluffier, more resilient original condition. The filing and needling of the hammers takes care of the three problems - grooving, flattening, and compaction - and gets them back to their smooth, rounded, and resilient younger selves. I schedule this service so that I have your piano's action for 24 hours or less. Often I am able to pick up the piano action from your home in the morning and return it to you at the end of the day.
My customers have remarked that my hammer voicing has transformed their piano's tone from harsh and raspy to warm, rich, and mellow. Please contact me if you'd like me to work with you on improving the quality of your piano's voice.