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Your Piano’s Innards, Outards and Major Components

Some piano owners just want to play the thing…well, hopefully. They’re too busy being concerned about the functioning of their own fingering and innards, while sitting at the keyboard, to care much about the movement of the springs, parts and mechanisms inside the piano. I understand. The inside of a fine Swiss watch is an amazing interlacing of precision gears and movements, but when I look at my watch, I just want to know the time.

But a modern-day grand piano is made up of some 9000 individual parts, many of them moving parts, and many people are fascinated by how it all fits together and “ticks.” These next posts are for you!

First lets take a look at an exploded view of a modern-day grand piano, and talk about the function of each component.


This shows the basic large components of any grand piano, minus the strings and tuning pins (which can be seen in the open-top view on the grand in our last post, The Modern Piano Emerges.)

The S-shaped outards of every grand are referred to as the piano’s case or rim. The straight bar of wood that across the front of the piano, directly over the keys, is called the “stretcher.” The wood that closes over your keys is called the “fallboard,” and there’s a couple blocks of wood on either side of the keys called “cheek blocks” and a long thin strip of wood just in front of your keys called the “key slip,” which round out the main furniture parts of the piano’s case. The stretcher is mortised into the piano’s rim, but the fallboard, key slip and cheek blocks are all easily removable, and you’ll see your technician quickly setting these furniture parts aside if he needs to access the action & hammers. As you can see by the photos above and below, on a grand piano, the keys & action just slide out of the front of the piano like a works-in-a-drawer. That’s important, because although tuning does not require action removal, virtually every other adjustment to the action and hammers does, so the technician has to be able to slide it out often and fast.

Grand Piano Action

We’ll take a look at the works of the piano’s action in our next entry. The soundboard and iron plate that seem to be floating above the piano in the top photo, are glued and bolted down inside the piano’s rim. After the strings are installed, they will pass over the treble and bass bridges and send their vibrations down through the bridges to the soundboard, which is the main sound-amplifying body of the piano. The heavy cast iron plate bears the tremendous tension of these strings (up to 20 tons) so the wooden case doesn’t need to.

If you look close at the front end of the iron plate in the top photo, you’ll see lots of little holes just in front of the red felt strips. You’ll see similar holes in the shelf of wood just behind the stretcher, called the “pin block.” These holes line up when the iron plate is bolted down into the piano, and the metal tuning pins are driven through the holes in the plate, down into the wooden pin block, to hold the tension and tuning of each string, as illustrated below.


As you can see, the inch-and-a-half thick pin block is multi-laminated and cross-grained for a super-firm hold on the tuning pin. That’s a good thing, as the tuning pins don’t “screw” into threads in the wood, but are held just by friction. How? The tuning pins have a very fine thread, giving them a “rough” surface, and they are precisely .010 (ten-thousandths) of an inch thicker than the hole they are being pounded into, when the piano is initially strung at the factory. That’s it! The pin’s just a little thicker than the hole, so it’s tight in there…but they can & do come loose after the pin block has been subject to either significant age (50-100 years) or significant dryness in low-humidity climates.

The top diagram shows how they pass through the holes in the iron plate (the greyish cutaway,) then down through the pin block holes, at about a 7º backward-leaning angle, to further support the immense pull of the string. The string is coiled about 3 full turn around the pin, with the tip of the string inserted into the tiny hole drilled through the pin (see above) called the “becket.”

To see how it all fits together, check back to that open-top view of a grand piano in the last post by clicking here. In our next entry, after the Holidays (hope you have a “Grand” season!), we’ll take a deeper look at the soundboard, bridges and action works.

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