Piano Bridge

Next time you have a chance lift the lid on a grand piano and look down inside. You'll see a large metal plate and pins anchoring the strings to it. This is the frame. Now look again and you will see two curved wooden constructions, typically following the sway of the frame, one at the front and one at the back with the strings passing over them. These are the bridges – a treble and a bass (the shorter one).

The best way to understand the bridge is to think of how a piano generates sound. You, the pianist, hit the key, which in turn causes a hammer to strike a string and make it vibrate. If it were just the string itself vibrating, the piano would generate a fairly weak sound. But, as we've seen with the soundboard, it's all about amplifying that sound you make. The bridge is a pathway for the vibration of the strings down into the soundboard, where the real amplification happens.

So the bridge's job is to transmit as much of the vibration as possible in as faithful a way as possible into the soundboard. It's like a pipeline for sound waves.

By now you likely know just how critical it is to choose the right material for the job. So it should come as no surprise that bridges are no different. The right wood is vital. As with the soundboard, some sort of hardwood is commonly used in higher end instruments. You'll find maple in a Bösendorfer and hard rock maple in a Steinway. Fazioli utilized a very unique bridge construction. Very similar to the original Hamburg Steinway's during their heyday, Fazioli bridges utilize rock maple and Brazilian Mahogany in vertical laminations. The maple is used to transmit the high frequencies due to maples very short grain composition. The mahogany is extremely long grained which allows for more efficient transmission of bass frequencies. This is a completely unique bridge design and is extremely expensive.

But because the bridge is a complex design it is made of composite materials. Look at the cap for example. This runs along the top of the bridge and is sometimes made of a different type of wood. On top of this there is often a graphite coating on which the strings rest. This allows for the vibrations to move more uniformly down into the soundboard.

Now it's not just what type of material you have, it's how you use it to get the best sound from your piano. This is where design comes in. Typically a low end piano won't have a soundboard of sufficient quality to justify an advanced bridge. But as quality increases all round (and the price of the piano goes up), bridge design becomes more elaborate. You might begin to see fancy designs like cantilevered bridges in high end instruments. Here's an example of the sort of complexity you might encounter. The Italian Fazioli piano has bridges built of laminated mahogany and maple. This is a design that was used by Hamburg Steinway for decades but no longer used probably because of prohibitive cost. Fazioli also uses caps made of maple for the bass and centre, hornbeam for the treble and boxwood for the high treble. Now why would they go to that much trouble? The Fazioli bridges are worth more than some entire Chinese uprights, but they believe to ensure faithful sound, as the frequency of the note rises so too should the hardness of the wood underneath.

Look at the notches on the bridge to enable the strings to pass over. Are they machine cut or hand-notched? Hand work will cost more but enable a better fit. Next look at how the bridge is attached to the soundboard; a sparing approach with limited attachment points will help the soundboard to resonate more freely.

Overwhelmed yet? You probably should be. The variations in bridge design and materials make the purchasing process complicated. Design and materials shape the loudness, duration and quality of the tone. Once more I recommend you sit down in a well-equipped showroom, examine some different pianos with different bridges, play them and listen carefully. Now ask questions about each piano and again listen!

At the end of the day you need a bridge that will be true to the sound you and piano make and that will transparently and faithfully transmit it to the soundboard.