Is the Piano a String or Percussion Instrument?
The piano is both. By how its sound is made, it’s a string instrument — felt hammers strike tuned strings. By how you play it, it acts like a percussion instrument — you strike a key and the note rings, then fades, with no way to shape it afterward. Most musicians land on the precise version: a struck-string keyboard instrument.
Why the piano is a string instrument
Every sound a piano makes starts with a vibrating string. Lift the lid of a grand and you’ll see them: roughly 220–230 steel and copper-wound strings stretched across a cast-iron frame under something like 20 tons of combined tension. Press a key and a felt hammer flies up, taps the string, and drops away, leaving the string free to ring. The soundboard underneath amplifies that vibration into the tone you hear.
In the formal language of instrument families, anything that produces sound from a vibrating string is a chordophone — the same big family as the violin, guitar, and harp. By that definition, the piano is unambiguously a string instrument.
Why the piano is a percussion instrument
Here’s the catch: a violinist bows the string and a guitarist plucks it, but a pianist does neither. You press a key, which strikes the string with a hammer. Striking to make sound is the defining trait of percussion — the same action as a mallet on a xylophone or a stick on a drum.
And once the hammer hits, your control ends. You can’t swell the note louder, add vibrato, or sustain it indefinitely the way a string or wind player can — the sound simply decays. That strike-and-fade behavior is why the xylophone, marimba, and piano all share a percussion temperament.
It shows up in practice, too: when a piano plays with an orchestra, it’s usually grouped with the percussion section or treated as its own keyboard part — not seated among the strings.
The official classification
Musicologists use the Hornbostel–Sachs system, which sorts instruments by how they make sound. Under it the piano is a chordophone (string family), specifically a “struck box zither.” In other words, the official scheme files the piano under strings, while explicitly noting that the strings are set in motion by striking.
So the system itself bakes in the contradiction everyone feels: string family, percussion action. Neither camp is wrong — they’re describing different halves of the same instrument.
So what is it, really?
The most accurate, least argumentative answer is that the piano is a keyboard instrument that produces sound as a struck-string — a percussion-string hybrid. “Keyboard” names the interface you touch; “struck string” names the physics underneath.
If you have to pick one word for a quiz: classification systems put it in the string family, but everyday orchestral practice treats it as percussion. Knowing why each answer is defensible is far more useful than memorizing one. For the full mechanical story of how the hammer, string, and soundboard work together, see How the Piano Works.
Frequently asked questions
Is the piano a percussion or a string instrument?
Both, depending on how you classify it. By how its sound is produced, the piano is a string instrument — felt hammers strike tuned strings. By how it is played, it behaves like a percussion instrument — you strike a key and the sound begins to decay immediately, with no way to shape the note afterward. Music academics usually settle on "a struck-string keyboard instrument."
Is the piano a keyboard instrument?
Yes — "keyboard" is the everyday family the piano belongs to, alongside the organ, harpsichord, and synthesizer. But "keyboard" describes the interface (a row of keys), not how the sound is made. That is why the deeper string-vs-percussion question still comes up.
Why do people say the piano is percussion?
Because you make sound by striking — pressing a key throws a hammer at the strings, just as a mallet strikes a marimba or a stick strikes a drum. Once the hammer hits, you cannot bend, swell, or sustain the pitch the way a violinist or singer can. The note simply rings and fades. That strike-and-decay behavior is the hallmark of percussion.
Does the piano actually have strings?
Yes — a lot of them. A full-size piano has roughly 220–230 strings stretched across a cast-iron frame at tremendous tension. Low notes use one or two thick copper-wound strings; most notes use three strings tuned in unison, which is why a piano sounds full and slightly chorused.
How is the piano officially classified?
Under the Hornbostel–Sachs system used by musicologists, the piano is a chordophone — an instrument whose sound comes from vibrating strings — and more specifically a "struck box zither." So in the formal scheme it lands in the string family, with the playing action noted as struck (percussive). The two ideas are not in conflict.
Where does the piano sit in an orchestra?
When a piano appears in an orchestral score it is usually grouped with the percussion section or treated as its own keyboard part, not seated with the violins and cellos. So in practice orchestras treat it more like percussion, even though its strings make it a chordophone on paper.