Pianos

Last updated: July 8, 2010.

Who are the world's best musicians? Everyone has their own personal view on this, but for my money concert pianists win hands down. If you've ever seen a world-class pianist playing a great piece of music, like a Beethoven sonata, you'll understand exactly what I'm talking about. It takes amazing physical, intellectual, and emotional brilliance to play such a complex instrument in such a captivating way—and only a tiny proportion of the world's pianists are up to the job. But it's not just the musician who makes the music sound so fantastic: the instrument plays a huge part too. Let's take a closer look inside a piano and find out how it works!

Photos (left and right): On a high note: Steinway is generally considered to be the Rolls Royce of grand pianos. This is a superb Steinway grand dating from 1876 in the gallery at Lanhydrock, Cornwall.

How pianos make sounds

A piano sounds quite unlike any other instrument and, if you heard it on the radio, you'd probably never guess how it was making a noise. The confusing thing about a piano is that it's two different kinds of instrument in one: it's a string instrument, because the sounds are made with strings, but it's also a percussion instrument (like a drum) because the strings make sounds when something hits them. Listen to the music of a composer like Bartok and you'll often hear the piano being played percussively—almost beating like a drum!

So what happens when you press the key of a piano? The key is actually a wooden lever, a bit like a seesaw but much longer at one end than at the other. When you press down on a key, the opposite end of the lever (hidden inside the case) jumps up in the air, forcing a small felt-covered hammer to press against the piano strings, making a musical note. At the same time, at the extreme end of the lever behind the hammer, another mechanical part called a damper is also forced up into the air. When you release the key, the hammer and the damper fall back down again. The damper sits on top of the string, stops it vibrating, and brings the note rapidly to an end.

Artwork: How a piano works: Press down on a key and you make a small hammer shoot up and strike the corresponding strings from beneath. Release the key and the damper at the back falls down onto the strings, stopping the note. Note that this is a hugely simplified version of what happens. The hammer and the damper are actually controlled by much more intricate mechanisms than this. You can see just how intricate by looking at the Schematic of the Steinway Model M Grand Piano on the Steinway website. This artwork shows the action mechanism (which plays the notes) in full detail.

Soft and loud: piano et forte

If that were all their were to a piano, no one in the audience would hear very much. So there are lots of other parts in a piano designed to make notes sound louder or last longer. The strings of a piano stretch out horizontally away from the pianist sitting at the keyboard, just as though a piano were a guitar laid flat on its back.

When you pluck a string, it vibrates, sets air molecules in motion and sends the sounds of the strings out toward your ears. To make the sounds louder, there is a large piece of wood mounted underneath them, called the soundboard (or sounding board). When the strings vibrate, the soundboard also vibrates in sympathy (resonance), just as a wine glass vibrates when a soprano sings a high note nearby. The soundboard effectively amplifies the strings so they are loud enough to hear. The lid helps the audience too: sound from the strings and the soundboard travels straight up, hits the lid, and reflects out toward the audience. That's why it's always better to sit on the right of the pianist and why concert hall seats to the left of (and behind) the pianist are generally much cheaper.

Photo: Looking from the back of a piano, under the lid and into the case, you can see the strings stretched taut across the sturdy cast-iron frame. The long bass strings are on the right in this picture and the shorter treble strings are on the left. The open lid reflects the music into the audience like a giant, wooden sound "mirror". Picture adapted from an original photograph by Marie Cassetty courtesy of the Defense Visual Information Center.

How do the pedals change the sound?

While the 88 keys on a piano control the musical notes that the pianist can make, the three pedals determine how loud or soft these notes are and how long they last. The pedal on the left is called the soft pedal. Most of the keys on the keyboard hit two or three strings simultaneously when you press them, so you get a richer and louder note. However, if you press the soft pedal down, the hammers that play the notes shift slightly to one side so they contact fewer strings—making a quieter note. The middle pedal is called the sostenuto pedal: when you press it down, it temporarily deactivates the dampers for the notes that you're playing at the time, and makes them last quite a bit longer. The pedal on the right is called the sustaining pedal. Pressing it down raises all the dampers up in the air so all the notes last longer.

Photo: In an upright piano, like this vintage Steinway, the strings run vertically at the back of the case and the hammers strike them by moving horizontally. It's like a grand piano standing on its end—literally upright. This particular instrument spent 22 years entertaining naval personnel stationed onboard the nuclear submarine USS Thomas A. Edison. Picture by courtesy of Steinway & Sons and US Navy.

Strings and things

If you've ever wondered why pianos are such a funny shape, that's easy to answer too. Remember that they're string instruments. Lower notes need longer strings than higher notes, so the bass strings for the low notes on the left-hand side of the keyboard need to be much longer than the treble strings for the high notes on the right-hand side. That's why the case is longer on the left than on the right and why it has that funny curved rim. In fact, the strings on the left are so long that they cross over, on top of the middle and treble strings to save space. (Take another look at the photo up above.)

Since each note can have up to three strings, it turns out that there are well over 200 strings inside a piano—each one stretched really tight. To stop the strings from collapsing the entire piano inwards, the rim and case are reinforced by a huge, heavy cast-iron plate. The plate sits just above the sound board and large metal holes around its edge (known as rosettes or portholes) allow the sound to come up through it.

That's a very quick tour of a piano, one of the world's most amazing instruments!

Photo: Another view of the Lanhydrock Steinway Grand.

Further reading

Books

• Barron, James. Piano: The Making of a Steinway Concert Grand. New York: Times Books, 2006. A very readable little paperback that describes the fascinating story of how one Steinway piano was put together, starting from the forest that supplied the trees and ending in the concert hall where the instrument made its musical debut.