The piano is one of the most complex and fascinating musical instruments ever created. With over 12,000 individual parts and centuries of craftsmanship behind its development, the inner workings of a piano reveal a story of engineering, acoustics, and artistry. When you lift the lid of a piano, whether upright or grand, you’re not just seeing wood and strings—you’re looking at a meticulously designed machine built to convert a musician’s touch into a wide spectrum of sounds.
In this article, we will explore in detail what the inside of a piano looks like, breaking it down into its major components, discussing the differences between upright and grand pianos, and providing insight into how each part contributes to the instrument’s overall function. Whether you’re a beginner pianist, an experienced musician, or simply curious about the mechanics behind this iconic instrument, this comprehensive guide will give you a clear and detailed understanding of what makes a piano work.
The Basic Anatomy of a Piano
Before diving into the internal structure, it’s important to understand the overall layout of a piano. Most pianos fall into two main categories: upright pianos and grand pianos. While both types produce sound through the same basic mechanism—felt-covered hammers striking strings—the orientation and layout of their internal parts differ due to the design.
Despite these design differences, both types of pianos share core internal components:
- Keyboard
- Action mechanism
- Hammers
- Strings
- Soundboard
- Bridge
- Pinblock
- Dampers
- Pedals
Let’s now take a deeper look into each of these components and how they appear inside the piano.
1. The Keyboard: The Gateway to the Piano’s Interior
At the front of every piano, you’ll find the keyboard, consisting of 88 keys on most modern instruments. These keys are made of either wood or plastic and act as levers. When a key is pressed, it initiates a complex chain of internal reactions inside the piano.
Beneath each key, a mechanical linkage connects the key to the action—the mechanism that transfers the motion of the key into the motion of the hammer striking the string. Although not visible from the outside, the underside of the keyboard is intricately connected to the action components, which lie just behind or above it (depending on the type of piano).
2. The Action Mechanism: The Heart of the Piano
The action is arguably the most intricate part of a piano’s interior. This assembly of levers, springs, pivots, and other moving parts is responsible for converting the downward motion of a key into the controlled movement of a hammer that strikes a string.
In an upright piano:
The action is mounted vertically behind the keys. When a key is pressed, it pushes a lever (called a whippen) upward, which in turn causes a jack to push the hammer toward the string.
In a grand piano:
The action lies horizontally beneath the strings. Gravity helps the hammers return to their resting position, allowing for quicker repetition and better control.
Key parts of the action mechanism include:
Whippen: A pivoted lever that transfers motion.
Jack: A small part that pushes the hammer forward.
Repetition lever (in grand pianos): Allows fast repetition of notes.
Let-off button: Controls how close the hammer comes to the string before release.
When you look inside a piano, especially a grand, you’ll notice rows of these precise mechanisms aligned side by side, each connected to a key.
3. The Hammers: Striking the Right Note
The hammers inside a piano are small mallets made of wood and covered with thick felt. When activated by the action mechanism, they strike the strings to produce sound.
Each hammer is carefully shaped and voiced (hardened or softened) to create the ideal tonal quality. In the interior of a grand or upright piano, you’ll see:
88 hammers (one for each key), though some notes share strings (more on that below).
A curved rail or hammer shank from which they are suspended.
Careful alignment so that each hammer strikes its respective strings at the correct angle and point.
Over time, these hammers wear out and need reshaping or replacement. Observing a used piano inside will often reveal grooves in the felt of each hammer—evidence of decades of playing.
4. The Strings: Where Vibration Meets Sound
One of the most striking visuals when you look inside a piano is the massive array of strings. These steel wires are stretched tightly across a metal frame and differ in length and thickness depending on the pitch they are meant to produce.
Key observations when viewing piano strings inside:
The bass strings are longer and thicker, and often wound with copper to increase mass.
The treble strings are shorter, thinner, and unwrapped.
Each note usually has:
One string for the lowest 10–15 keys (single string per note).
Two strings for mid-range notes (bichords).
Three strings for upper-range notes (trichords).
This design helps produce a rich, full sound across the instrument’s range. Strings inside a grand piano run diagonally from the upper right to the lower left (when viewed from the front), while upright piano strings are mounted vertically.
5. The Soundboard: The Piano’s Amplifier
The soundboard is the large wooden plate that lies beneath the strings. When the strings vibrate, they transfer that vibration through the bridge into the soundboard, which amplifies the sound.
Made of spruce and slightly arched (crowned), the soundboard is responsible for the piano’s tone and resonance. In the interior of a grand piano, it lies flat beneath the strings. In an upright piano, it stands vertically at the back.
The soundboard’s visible features include:
Ribs: Wooden slats attached to reinforce and maintain its curvature.
Bridge: A thin wooden rail (actually two—one for bass, one for treble) that the strings rest on.
Grain direction: Running perpendicular to the bridge for optimal vibration transfer.
When viewing the inside of a piano, especially with the bottom panel removed (in uprights), the grain, ribs, and craftsmanship of the soundboard can be admired.
6. The Bridge: Connecting Strings to Sound
The bridge inside a piano is not to be confused with a violin or guitar bridge. In a piano, the bridge is a hardwood strip (often maple or beech) that sits atop the soundboard. Strings are tightly pinned against the bridge, which transfers their vibrations down into the soundboard.
There are typically two bridges:
Bass bridge: Shorter, curved, often offset to the left.
Treble bridge: Longer, straighter, located more centrally.
The placement of the bridges is carefully calculated to ensure accurate intonation and efficient sound transmission. On a grand piano, you can view the bridges by removing the top lid and looking down through the strings.
7. The Pinblock and Tuning Pins: Holding the Tension
At one end of the strings inside a piano, you’ll find the tuning pins embedded in the pinblock (or wrest plank). The pinblock is a multilayered hardwood panel designed to grip the tuning pins tightly and withstand the tremendous tension of the strings.
Each tuning pin holds a string and can be turned slightly using a tuning lever to adjust the pitch. A modern piano exerts a total string tension of over 20 tons, so the stability of this component is critical.
When you lift the lid of a piano, especially a grand, the row of steel pins in the pinblock is one of the first things you see—typically at the front of the instrument, above the keys.
8. The Dampers: Stopping the Sound
The dampers are felt-covered blocks that rest against the strings when the keys are not being played. Their role is to mute the strings, stopping them from vibrating after the key is released.
Inside a piano, dampers are clearly visible above or beside the strings (depending on the type). They are:
Lifted off the string when a key is pressed, allowing the note to ring.
Reapplied to the string when the key is released.
The right pedal (sustain pedal) lifts all the dampers at once, allowing multiple notes to ring together. When you look inside a piano and press a key, you’ll notice the damper lifting and the hammer striking the string.
9. The Pedals: Controlling the Inner Mechanics
Modern pianos typically have three pedals, each connected to internal mechanisms that modify the sound or response of the instrument.
Right (sustain) pedal: Lifts all dampers.
Middle (sostenuto) pedal: Sustains only the notes currently held (mainly in grands).
Left (soft/una corda) pedal:
In grand pianos, shifts the entire action and keyboard to strike fewer strings.
In upright pianos, moves hammers closer to the strings, reducing volume.
Under the piano, you’ll see rods or levers connected to the pedals. These connect to internal wooden or metal linkages that engage the necessary parts when a pedal is pressed.
Differences Between Grand and Upright Piano Interiors
Though both use the same basic mechanisms, the layout and accessibility of internal parts vary greatly:
| Component | Grand Piano | Upright Piano |
| String Position | Horizontal, diagonal | Vertical |
| Action | Below strings, gravity-assisted | Behind keys, spring-assisted |
| Soundboard | Horizontal beneath strings | Vertical at back |
| Hammer Movement | Horizontal (strikes upward) | Vertical (strikes forward) |
| Repetition Speed | Faster due to gravity and repetition lever | Slower due to spring action |
These differences also affect maintenance. For instance, voicing or regulating an upright piano typically involves removing the front panel, while grand pianos allow easier top-down access.
Conclusion
The piano is far more than just keys and strings. Its inner structure is a blend of precise engineering, time-honored woodworking, and artistic tuning. Whether you play daily or are simply an admirer of fine instruments, understanding what lies inside a piano enriches your appreciation of its sound and craftsmanship.
The next time you hear a haunting nocturne or a booming concerto, remember that behind each note lies a vast network of hammers, strings, wood, and metal—working in harmony, hidden in plain sight.
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