An Essential Element Holding the Tension of the Strings
Frame, Back Posts

Function and Construction

• Together, the frame and back posts withstand and support the combined string tension. A piano has approximately 230 strings, and with each string tensioned at approximately 90 kg, the total tension is in excess of 20 tons.
• The back posts and frame are extremely resistant to bending and twisting, enabling them to firmly support this tremendous tension. This stabilizes the soundboard, ensuring it will continue to produce Yamaha's beautiful "singing" tone for many, many years. The strength of the back posts and frame has a major influence on the quality of the sounds.
• Not only do the back posts and frame support the tension of the strings, but by vibrating together with the strings, also affect overall sound quality.





Materials

• The frame is high quality iron casting. The hardness, shape and thickness all subtly affect the sound.

Design and Fabrication Technology

• Yamaha stresses the importance of a tough and durable frame that is not easily affected by either temperature or humidity changes.
Therefore, the frame and back posts have been designed to act together as a single unit, supporting and withstanding the tremendous tension of the strings.
• For its frames Yamaha has developed the latest in casting technology: the world's first vacuum shield mold process (V-process). This V-process enables Yamaha to produce its own extremely high quality piano frames. The support of this technology has made it possible for Yamaha to design and produce piano frames that are the envy of the industry.
• The V-process is the world's most advanced frame casting method. Using plastic film and vacuum to hold the sand in position rather than the traditional wet sand method enables Yamaha to produce very high quality piano frames.
• Realizing that casting of piano frames requires very sophisticated techniques as well as advanced and well equipped facilities, Yamaha invested heavily in creating a new type "clean" foundry. We are one of the few piano manufacturers in the world that produces every piano frame it uses. Most of the other manufacturers purchase all, or at least part of their frames from outside foundries.