Casting a concert piano.

Making a piano is a complicated process. There are hundreds of tiny sections--front the soundboard to each individual string--that have to be just perfect in order for the instrument to function in tune. To ensure that so many individual components can come together, the piano needs a stabilizing force, which is where a casting comes in.

In every Steinway piano is a large cast iron plate that provides a rigid and stable foundation needed to hold approximately 40,000 lb of string tension. Each plate has to be manually lowered into the piano case and fitted to ensure a precise fit. If the plate is even slightly out of alignment, it can cause the strings to go out of tune.

When building a piano, each string is inserted into a turning pin, wrapped three times and then placed through one of the more than 200 holes in the cast iron plate. "Because of the large amount of force exerted by the strings, a piano calls for an engineered material that can stand up to high levels of force for long periods of time," said Bob Berger, director of quality at Steinway & Sons, Long Island, New York.

When Steinway first began making pianos in 1853, the cast iron plates were made in an inhouse foundry. "We did our own casting until 1939, when the city of New York placed restrictions on foundries inside the city limits," said Berger. Today, Steinway buys its castings from its subsidiary foundry, O.S. Kelly Co., Springfield, Ohio. The firm casts plates for both the Steinway offices in New York and Hamburg, Germany.

There are seven different types of iron plates due to the two different types of pianos (grand and upright), which are produced in different sizes. While all plates are cast in a grade 30 gray iron, two different processes are used. The smaller plates are cast via green sand molding, while plates used in the larger concert grand pianos are produced via nobake. "We have an automatic molding machine for the smaller plates," said Berger. "The plates featured in our larger pianos cannot fit on the line so we use the nobake process."

The cast iron plate started out as a simple flat plate in the original Steinway pianos, but has evolved over the years. Today, it is one of the most important aspects of the piano. "A piano is all about scale, and in order to achieve that scale you need to be extremely precise on the length and strength of the strings," Berger said. "The cast iron plate is one of the most crucial elements."