Under Pressure!

Today, we put forth a short post dedicated to just how amazingly engineered the piano is. We all have some sense of how exactly a piano functions–when a key is pressed, it raises a hammer, which strikes a set of 1-3 strings, which produces sound through vibration. That in and of itself is the most rudimentary description I can come up with, however, in future posts, we’ll be getting far more technical. Okay, so this begs an answer to the question: why are pianos so damn heavy? The answer in simple terms: because they have to be.

The piano is made up of over 200 strings–some notes have only one string (the bass notes), some have 2 strings tuned in unison (bass/tenor notes)  and the majority have three strings tuned in unison (the treble notes). The lower bass and tenor strings are made up of steel cores, wound tightly with either brass, or in older pianos, silver. Pianos with silver wound strings are extremely rare, and replacement strings are nearly impossible to come by. The treble notes are made up of the same gauge steel, and pitch is affected by how long or short the string is, as well as tension placed on the string.

Here’s the fun part: with all strings tuned up to their respective pitches, the strings themselves exert anywhere from 18-30 TONS of pressure on the metal plate holding them in place. That’s over 60,000 pounds of pressure, or the weight of 30 elephants, contained in a wooden box.

To put this in perspective–if you were to take the lowest string on a piano (A-0) and string it from the top of the ceiling of your house to the floor, and had a way to adjust the tension, the tension of the string would collapse your house before it were to reach 1/2 of its normal pitch.


To compensate for the enormous amount of pressure put on the body of a piano by its strings, pianos are specially outfitted with an [extremely heavy] cast iron plate that takes the brunt of the squeeze. In addition, the strings are wound around steel tuning pegs that are mounted into a piece of wood known as the pin block. The pin block is made up of several pieces of hard wood glued together with alternating grain directions (for extreme strength) and drilled out to accomodate tuning pins. The final result of the construction of the pin block is a piece of wood almost six inches thick, weighing almost 60 lbs.

This is the cast iron backplate for an early 1930's Vose and Sons upright grand piano. Note all of the construction elements mentioned earlier.

Early pianos did not have the luxury of cast iron plates, and so had strings under much less tension, which produced a much weaker sound. Todays powerful concert grands can fill a hall with rich and powerful sound, but do so at the cost of weighing over 800 pounds.

Find out why it’s so important to keep your piano tuned regularly in the next post!


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