Important Factors Determining the Balance of the Tone and VolumeHammersFunction and Construction
• Sound is produced by striking the piano strings with the hammers, causing the strings to vibrate. When striking the strings in the middle register, the hammer is in contact with the strings for approximately 1/880th of a second.
• The hammers are constructed by attaching one or two layers of felt onto a hardwood core.
• The hammer uses high quality felt made from the wool of sheep.
• In the final step of preparing the sound, the felt is given further attention by the voicer to adjust the overall sound. The hammer greatly influences the sound quality. Even changing the density of the felt slightly with needles will cause the piano's sound to change.
• The hammer heads must maintain their resilience and not deform--even after hundreds of thousands of impacts.
• Each model superior to and including the U3AS, uses a hammer that consists of two layers of felt throughout all 88 hammers. Underneath the top felt is another layer of felt (underfelt), making it possible to fabricate the larger hammers needed for the larger pianos and obtain the correct density the designer specified. This especially increases the strength and impact of the lower registers creating an overall beautiful, and richer tone.
• The U1A, being smaller pianos than the U3AS, use hammers that have underfelt in the 60 or so largest hammers, and single layer felt in the smallest hammers above that. This special fabrication approach allows the hammers to contain the characteristics needed for each individual scale.
Materials• The characteristics of the hammer felt varies greatly, according to the origin of the wood. Much research and technology is required to form the uneven wood into even and uniform hammer felt.
• The quality of the felt is also an important factor affecting the overall sound.
• Yamaha only uses those materials (felt, wood, etc.) that have been exclusively selected and made for Yamaha hammers.
• Stringent standards are in effect concerning the hardness and thickness of the felt. Therefore, it is not easily affected by the climate, and it is extremely durable.
Design• The best hammers are those that have been matched to the piano itself. The optimum mass, shape and resilience should be designed not only in consideration to how well it matches the action, but to the strings and the sound board as well.
• Each Yamaha piano model has hammers especially designed for it-hammers that have the correct mass and shape for that particular piano.
• The ideal hammer felt is soft on the surface and gets progressively harder towards the center. However it is very difficult to control the felt so that it has the ideal elasticity.
• Yamaha developed a special device that can measure the hardness of the hammer felt at any point from the surface to the core. Now, the felt elasticity can be controlled according to the original design, all the way to the centre.
Fabrication Technology• Attaching the felt onto the hammer wood requires highly advanced techniques and over ten tons of pressure.
• By using its own in-house developed, specialized machinery, Yamaha produces high quality and uniform hammers.
• Throughout the world, piano manufacturers who craft their own hammers are rare.
