Piano Rim

The piano's direct ancestor is the harpsichord. If you look inside one, you'll see that the harpsichord's workings are housed in what is essentially a wooden box with (depending if it was a lightweight Italian or a sturdier Flemish instrument) a little bit of reinforcement. Usually it was made to look pretty to fit in with the rest of the household furniture. This is fine for the delicate sounds of the Baroque era – think of J.S. Bach's English Suites, but it would be a design challenge later on when the likes of Beethoven would hammer out Romantic music on a keyboard.

From the day in 1710 when Bartolomeo Cristofori, a harpsichord maker in Padua (near Venice), built the first of what he called a ravicembalo col piano e forte – or "harpsichord with soft and loud", the struggle has always been to craft an instrument that would enable greater range of expression. By the time the Romantics hit the scene, the piano was becoming a more massive – a more expressive, instrument. For example, Beethoven's favourite piano-maker, the Englishman John Broadwood, added an octave to the piano's range and increased the tension of the strings.

The harpsichord's fancy box with pretty pictures was no longer a viable option for the piano's case. In order to prevent the highly-stressed piano from folding up like an accordion under the strain of so much string tension, the rim of the piano had to play a structural role instead of a purely decorative one… which brings us to a discussion of the essential qualities of this part of the instrument.

Wrapping around the "guts" of the piano is what I've been calling the rim – a flowing wall about a foot in height, often a nice glossy black. You probably know it for the characteristic wing shape it gives to the grand or baby grand piano (useless fact: did you know that, in addition to uprights and grands, there used to be a square piano shape?).

To continue with the car analogy, the rim is the body of the piano. Just as with car bodies, most people don't pay much attention to how the rim is built or what it's made of. This is unfortunate because no other part of the piano has such an influence over the lifespan of the instrument and the projection of sound.

Let's talk tension first. We've already seen how string tension increased as the piano developed as an instrument. Today a typical grand piano's strings have a combined tension of 22 or more tons – about the weight of 12 elephants. It's a lot. So a modern piano rim does more than contain all the bits. It gives stability to the piano's structure.

But it does more. All the wonderfully expressive sound coming from the collision of hammers and strings should be projected outward into the room (whether your living room or a concert hall) and to the ears of the audience. In order to do this, the energy created by the pianist needs to be focused on the soundboard, not diffused to the other parts of the piano. The rim of your piano is one part of the construction that makes this happen – it should be dense so it doesn't absorb vibration energy. In short, a better, denser rim gives better sound.

Now let's see how rims are made and what makes a good one. Back in the day (1878 to be precise), Theodore Steinway of New York patented a new way of building a rim using layers of laminated wood. Nowadays this is the standard way of doing things. The differences are in the type of woods used, the number of layers and whether or not the layers are continuous. You'll find the Bösendorfer piano uses Bavarian or Carpathian spruce while the Baldwin and Steinway pianos are built of hard rock maple. In the Steinway factory piano rims are built up from 18 separate layers of this wood. Over at the Bechstein plant an outer rim of low-density hardwood is married to an inner rim of high-density hardwood, usually beech. Kawai has now become the only mass producer to use a hardwood rim on its RX series grands which gives it an unquestionable advantage. But a Pramberger or Samick made piano or most Chinese built pianos will have a rim made of softwood layers which ultimately effect longevity and tonal quality. Whatever the wood choice and layering approach, the rim is bent in a press to give it the wing shape of a grand piano.

No one is expecting you, the pianist, to be an expert in wood fabrication techniques. But it is essential to be aware of how choices affect the sound and longevity of an instrument. The best way to see and hear this is to visit a well-equipped showroom and "test drive" pianos with different rim constructions to hear the difference. A good piano technician will also help you sort of what rim is right for your needs and budget.