Piano Strings and How They Work

When you press a key on a piano, a hammer strikes a string, making it vibrate. If you hold the key down, the string will keep on vibrating. And if you hold down the damper pedal, the string's vibration will cause other strings to vibrate in sympathy. This is called "sympathetic vibration" and it's part of the reason for the piano's richness of sound.

If you look inside a piano, whether it's an upright or a grand, you'll notice that these instruments come in a wide range of shapes and sizes, from compact uprights to baby grands to concert grands. They're made from different materials too, with prices from a few hundred to many thousands of dollars. And yet, despite these variations, they all have one thing in common. Without the dozens of strings inside, they wouldn't make the typical piano sound that's so universally loved and instantly recognizable.

A standard piano with a full keyboard has 88 keys. Treble notes have three strings each, mid-range notes have two strings each, and bass notes have one string each. That means there can be as many as 236 strings twanging away inside the instrument.

To fit all of these strings into the modern and more compact piano design, strings are often overstrung, as in the picture below. Here you can clearly see that there is one string for bass notes on the far left, then two strings for the mid-range or tenor notes, with the treble notes having three strings each. If you ever wondered why tuning a piano seemed like such a complicated process, now you know. For every note with 2 or 3 strings, each of the strings has to be tuned separately.

The lowest notes on the piano are the bass notes. They're deep and rich in sound, yet only require one string. But as you can see in the picture below, bass strings are very thick. That's because they're really two strings in one, a thin core wire with a thicker copper wire wrapped around it. The reason for this design is simple: if the bass strings were made of a single wire, they'd need to be about 25 feet long to produce the same depth of sound. Pianos are already pretty large, but just imagine how big they'd have to be to fit 25-foot strings in them.

As with any stringed instrument, the thicker and longer the string, the lower or deeper the note it will produce. Unlike the bass and mid-range strings, treble strings need only a single piano wire to create the right sound. But to make that sound as rich and luxurious as possible, three identical strings are used.

Why? Well, think of a standard 6-string acoustic guitar and then compare it to a 12-string version. The latter has a fullness of sound that can only be achieved if two 6-strings play together.

Likewise, if the treble strings on a piano were all single strings, the result would be a thin and unsatisfactory sound, particularly in comparison to what we're used to hearing.

In the picture below you can see an example of the bass and mid-range strings next to each other. Notice how the dampers rest against the strings. For bass strings, the felt dampers are v-shaped to surround the strings while dampers for mid-range strings go between the two strings.

Here's what happens when a key is pressed:

• The hammers (also pictured below) are thrown forward
• They strike the string(s)
• At the same time, the dampers are released to let the string(s) vibrate
• If the key is held down, the damper stays away from the string, letting it vibrate
• If the hammer is released, the dampers fall back and rest against the stringa again

In the animation opposite you can see an example of a typical piano action. The word "action" refers to the way the keys, hammers, and dampers operate whenever a note is played. The harder you press the key, the harder it strikes the string, and the louder the sound produced. This is the same basic mechanism that was devised by Barolomeo Cristofori back in the 1700s.

Most pianos have at least two pedals, typically called the soft pedal and the sustain pedal. The soft pedal (or una corde) is on the left, and the sustain or damper pedal is on the right. These two pedals affect the sound of the piano by altering the way the strings are struck. Here's how it works.

When the left-hand pedal (or soft pedal) is pressed, one of two things happens.

1. On upright pianos, the hammers move closer to the strings. This means they strike the strings with less force, i.e. softer, which makes the resulting sound softer as well.
2. On grand pianos, the hammers move sideways. This means that for single bass strings, they strike the strings on a lesser-used part of the hammer. For treble strings, the hammers strike two strings instead of three, producing less of a sound and making it quieter.

When the damper pedal is pressed, it lifts all the dampers away from the strings. This means the strings are free to vibrate and resonate freely, making it possible to produce an enormous amount of sound that rings on until the pedal is released or the sound fades away naturally.