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How Do Piano Keys Make Sound?

Eight-year-old Gretchen from South Burlington, Vt. asks, "How do piano keys make sound?"

Did you know pianos have strings and hammers? We're learning all about instruments and how they use strings to make noises.


Pianist Annemieke McLane shows us the inner workings of a piano, and cellist Emily Taubl shows us how strings and stringed instruments make sounds. Plus we learn how record players make sound.

"How do piano keys make sound?" — Gretchen, 8, South Burlington, Vt.

"The piano is like a huge frame that is the shape of the piano. Then you have the soundboard. The soundboard is sort of the bottom of the piano. The soundboard is like the back of the cello or the back of the violin or bass, you need some resonance. Without a soundboard, the sound won't go anywhere.

"When you look at the key itself, it's just a white and black stripe. The key is a lever, basically. And it rests in the middle on a little wooden block and then there is a screw pilot and it pushes a whole bunch of little [pieces], almost like if you would be a surgeon, you would see all the little bones.

"It almost looks like a hand inside. Then one thing starts to move, and the other thing starts to move, and the roller rolls, and the roller rolls the hammer up and then the hammer shoots up against the string, and the damper shoots up. And so everything comes in motion at once," explained Annemieke McLane, a pianist.

Credit Brent Harrewyn
Annemieke McLane is a pianist originally from the Netherlands, now living in Vermont, where she performs and teaches.

A piano has about 230 strings, and it's those strings that actually make the sound of a piano. So when you're looking at those black and white piano keys, they're attached to various pieces that are connected to a little hammer. When you push down on the piano key the hammer is pressed against one of those strings or sometimes it takes two or three strings together to make the sound of one note.

"So what happens is that when you play, you push a key down you trigger a whole mechanic and there is that hammer underneath the strings, that comes up and hits those three strings all at once, or two, or the one big thick one, and you hear a sound. And then when you let the key down, I release it, the sound stops. These are called the dampers.

"The length of the strings makes the pitch higher or lower. At the right side of the piano the strings are quite short and thin," and at the other side of the piano is the bass strings, which are so long, they are usually put in diagonally and they are extra thick. "So it's basically the length of the strings and the thickness that makes the pitch different." 
— Annemieke McLane, pianist

"How do strings make noises?" — Kelsie, 4, Redlands, Calif. "How do stringed instruments make sound?" — Franka, 9, Edmonton, Alberta

Credit courtesy from parents
Gretchen, left, lives in South Burlington, Vt. and is 8 years old. Kelsie, center, is 4 years old and lives in Redlands, Calif. Anita, 6, is from East Calais, Vt.

"I think just to address the idea of a string in general, it can be made out of lots of different materials. And basically, it's probably quite thin and you stretch it as tight as you can. And then if you pull on it depending how tight it is it will make a pitch, it will make a sound because it's vibrating. If it's pulled really tightly the vibrations can be wide or small and make a higher pitch or a lower pitch."

"As far as strings on a string instrument, like my cello, I have four strings and the higher pitch strings are very thin and then they get thicker as they go towards the bottom of the instrument as the pitch goes lower. So they're all pulled very, very tightly across a piece called the bridge which sits in the middle of the instrument and holds the strings off of the instrument. The higher string is very thin. And then a lower string is quite fat, so it makes that deeper richer sound, because it vibrates at a slower speed.

"The strings come up to the top of the instrument and they're wrapped around what we call pegs, and to tune the cello or the violin or the viola or the guitar, all the string instruments, we turn the pegs so if we want the pitch to go up we'll tune the peg up. So we pull the string tighter. And if we want the pitch to go down we just turn the peg down and let it be looser."

"The body of [the instrument is] called the sound box. Because the strings are wrapped around in the pegs and connected to the bottom of the instrument, when they touch the bridge the bridge starts to vibrate. And then that makes the top of the instrument start to vibrate. So the sound box and the bridge are both vibrating and basically the air inside the instrument also starts to vibrate. So we have these holes carved on the front of the instrument and that lets the sound escape. They're called F holes because they're kind of carved like a cursive F and then the sound can escape from there."

"A bow is a stick of wood. It's a special kind of wood that you find in Brazil called pernambuco wood. The reason we use it is because it's a little bit flexible. And then the wood is connected to a bunch of horse hair. So it's the hair from a horse's tail and it's white and we string it really tightly. And when we cross the strings that's what makes sounds." 

— Emily Taubl, cellist

Credit Karen L. Photography
Pianist Emily Taubl lives in Burlington, Vt.

Listen to the full episode to hear the instruments, and to learn how records make sound.

Read the full transcript.

Melody is the Contributing Editor for But Why: A Podcast For Curious Kids and the co-author of two But Why books with Jane Lindholm.
Jane Lindholm is the host, executive producer and creator of But Why: A Podcast For Curious Kids. In addition to her work on our international kids show, she produces special projects for Vermont Public. Until March 2021, she was host and editor of the award-winning Vermont Public program Vermont Edition.
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