How the Piano Works: Hammers, Strings, Pedals and Middle C

Press a piano key and a lot happens in a fraction of a second. A small felt hammer is thrown at a set of tightly stretched steel strings, bounces away so the strings can ring, and a damper waits to silence them the moment you let go.

Knowing how that machine works will make you a more thoughtful player: you will understand why holding a key changes the sound, what the pedals are really doing, and why the keyboard looks the way it does. Let's open the lid.

An Italian invention: soft and loud

Before the piano, the most common keyboard instrument in European homes and courts was the harpsichord. Its keys pluck the strings with small quills, so no matter how hard or gently you press a key, the volume stays almost the same.

Around 1700, Bartolomeo Cristofori, an instrument maker working for the Medici family in Florence, solved that problem. Instead of plucking, his instrument struck the strings with hammers, so a gentle touch produced a soft note and a firm touch produced a loud one. He called it a gravicembalo col piano e forte, roughly "a harpsichord with soft and loud". That mouthful was shortened to pianoforte, then simply piano.

Over the next two centuries, builders added more keys, heavier strings and a cast-iron frame to hold their enormous tension. By the late 1800s the modern piano had settled into the form we know: 88 keys, from a deep A at the bottom to a high C at the top, covering just over seven octaves.

Inside the action: from key to string

The set of levers between your finger and the string is called the action. Here is what happens, step by step, when you play a single note:

The faster the hammer is moving when it strikes, the louder and brighter the note. That is what pianists mean by "touch".

Most notes actually have more than one string. In the middle and upper range, each key strikes three strings tuned to the same pitch, which gives a fuller sound. In the bass, notes use fewer, thicker strings wrapped in copper wire so they can vibrate slowly enough to produce low pitches without needing to be impossibly long.

The damper lifts. A felt pad that normally rests on the string rises out of the way so the string is free to vibrate.
The hammer flies. A felt-covered hammer is pushed toward the string. Just before it arrives, a part called the escapement releases it, so the hammer travels the last tiny distance on its own momentum.
Strike and rebound. The hammer hits the string and immediately falls back. Staying in contact would choke the sound; this free-flight idea was Cristofori's key insight.
The string rings. Its vibrations pass through a wooden bridge into the large, thin soundboard, which moves much more air than a string could alone. That is what makes the note loud enough to fill a room.
Release. When you lift your finger, the damper drops back onto the string and the sound stops.

The three pedals

Most pianos have three pedals, and each one changes how the action behaves.

Right pedal (sustain or damper pedal). The most used by far. It lifts all the dampers at once, so notes keep ringing after you release the keys. Holding it through changing chords blurs everything together, so lift and re-press it as the harmony changes.
Left pedal (soft pedal). On a grand piano it shifts the whole action slightly sideways so the hammers strike fewer strings, giving a quieter, softer colour. This is why it is also called the una corda ("one string") pedal. On many upright pianos it moves the hammers closer to the strings instead, which has a similar softening effect.
Middle pedal. On grand pianos this is usually the sostenuto pedal, which sustains only the notes you were holding down when you pressed it. On many upright pianos the middle pedal instead lowers a strip of felt between hammers and strings to make practice much quieter.

Reading the keyboard: a pattern that repeats

The keyboard is really one small pattern repeated over and over. Look at the black keys: they come in groups of two and groups of three, alternating all the way along.

The white keys are named with the letters A to G. Once you reach G, the names start again at A. Every white key sits in the same position relative to the black keys, so:

From one C to the next C is an octave: twelve keys in total, seven white and five black. The higher C vibrates twice as fast as the lower one. Learn the layout of one octave and you have learned the whole keyboard.

Finding middle C

Middle C, also written C4, is the C closest to the centre of the piano. On a full 88-key piano it is the fourth C counting up from the bottom, and on most acoustic pianos it sits roughly in front of the maker's name. It is the meeting point of the treble and bass clefs in written music, so it is the natural home base for beginners.

C is always the white key just to the left of a group of two black keys.
F is always the white key just to the left of a group of three black keys.
The black keys are the sharps and flats in between, such as C sharp (also called D flat).

Try it now: your first five-finger exercise

You can do this on any piano or keyboard, or on the free online piano, where the A key on your computer keyboard plays middle C and A S D F G play C, D, E, F and G.

When that feels comfortable, try the same exercise with your left hand, placing your little finger on the C below middle C. If you want to step beyond five notes, the scales and chords reference shows the C major scale and the chords built from it, and HarmonyHub's beginner tutorial walks you through your first melodies.

Find middle C and place your right thumb on it. Number your fingers 1 (thumb) to 5 (little finger).
Let each finger rest on its own white key: 1 on C, 2 on D, 3 on E, 4 on F, 5 on G. This is called C position.
Play slowly up and back down: C D E F G F E D C. One note per beat, every note the same length.
Set a metronome to 60 beats per minute and play the pattern four times without stopping or speeding up.
Now try it softly, then loudly. Notice how the speed of your finger, not its pressure, changes the sound.

Wrapping up

A piano is a percussion instrument and a string instrument at the same time: hammers strike, strings vibrate, a soundboard amplifies, and dampers and pedals decide how long each note lasts. Find middle C, play your five-finger pattern evenly, and you are already using everything his invention was designed to do.