How a Piano Actually Works: What's Inside

A piano is the most mechanically complicated thing in almost any home that has one — north of 5,000 parts working in the second between your finger and the sound. It's also, at heart, one simple idea executed beautifully: a key is a lever that throws a felt hammer at tight steel strings, and a big wooden diaphragm turns their vibration into music. Understanding that chain — even casually — makes every piano owner better at owning one, because suddenly the care advice stops being rules and starts being obvious. Here's the tour we give curious clients at the bench.

The chain of events, in order

The key. A long wooden lever balanced on a centre pin — press the front, the back rises. Everything else is what that rising back end sets in motion.

The action. The famous complexity lives here: dozens of small wooden and felt parts per note that catch the key's motion and convert it into a hammer throw. Its crucial trick is escapement — at the last instant, the mechanism lets go, so the hammer flies free at the strings and bounces off rather than pressing against them (which would choke the sound instantly). The action is also what lets a note repeat rapidly, and why a piano can whisper or thunder from the same key: it transmits not just that you pressed, but precisely how. When touch goes uneven or sluggish, this is the machinery being regulated.

The hammer. A wooden core wearing dense wool felt, and the piano's tone lives in that felt: fresh and resilient makes warmth, worn and compacted makes harshness — which is what voicing adjusts. Strike, bounce, done, hundreds of thousands of times.

The strings. Steel wire under fierce tension — collectively about 18 tonnes of pull across the instrument, which is why there's a cast iron plate inside holding it all. Most notes have two or three strings tuned in exact unison; bass notes get one or two thick copper-wound ones. Each string ends at a tuning pin, and the fit of those pins in their wooden block is, quite literally, whether the piano can hold a tune.

The dampers. Felt blocks resting on the strings, lifting when you press a key (so the note rings) and dropping when you release (so it stops). The right pedal lifts all of them at once — that's the whole magic of sustain.

The soundboard. The unsung hero: a wide, thin spruce panel the strings press against through wooden bridges. Strings alone are nearly silent — too thin to move much air — so the board is the amplifier, taking their vibration across its whole surface and pushing it into the room. It's built with a slight outward curve (crown) and it's the part Canadian seasons work on hardest.

Press a key and the whole chain fires in about a millisecond. That's the machine.

Why the machine needs what it needs

The care advice writes itself once the parts are visible. Tuning exists because 18 tonnes of tension meets a wooden, weather-breathing structure — pitch drifts as the soundboard swells and shrinks with the seasons, no matter who does or doesn't play. Humidity control exists because nearly every part above is wood, felt, or leather, and all three take Canadian air swings personally. Regulation and voicing exist because thousands of moving felt-and-wood parts wear with use, gradually and fixably. And the technician's 90 minutes (here's that visit, narrated) is essentially a maintenance pass over this whole chain — strings set, and the machinery listened to.

The takeaway worth keeping: a piano isn't fragile, it's alive to its environment. Treat the room right and play it often, and the 5,000 parts mostly just work — for decades.

Common questions

How many strings does a piano have?
Around 230 for 88 notes — most notes carry two or three strings tuned in perfect unison, bass notes one or two heavier wound strings. That's also why tuning takes about 90 minutes: every string is set individually.

What's the difference between how uprights and grands work?
Same chain, different geometry: a grand's strings and soundboard lie flat and its hammers strike upward, letting gravity reset the action — which is why fine grands repeat notes faster. Uprights turn the whole assembly vertical to save floor space, using springs where the grand uses gravity.

Why does a piano go out of tune if nobody plays it?
Because the soundboard and structure move with humidity year-round, changing string tension whether the keys move or not. Playing is nearly irrelevant to tuning drift — the room's air does it. An unplayed piano drifts just as surely, only unheard.