How do guitar strings create different notes?

1. Leo strums his guitar. It has just six strings, yet he can play high notes, low notes and everything in between. How can six strings make so many different notes?
2. Pull a string to one side and let go. It springs back, shoots past the middle and swings back again, hundreds of times each second. That shaking is called vibration, and it is what you hear.
3. Press a string against one of the metal bars, called frets. Now only the part between your finger and the bridge can shake. A shorter piece swings faster, so the note is higher.
4. Each string wraps around a tuning peg. Turning the peg pulls the string tighter. A tighter string snaps back faster, so it shakes faster and sounds higher. This is how a guitar is tuned.
5. The strings are not all the same. The thick ones are heavy, so they are slow to get moving and they shake slowly, making low notes. The thin ones are light, shake quickly and make high notes.
6. A string by itself is thin and moves very little air, so it is quiet. The bridge passes its shaking to the guitar's thin wooden top. That big surface pushes a lot of air, and the sound pours out.

Tap each part of the guitar. Watch what it does to the strings and the sound.

• Strings. The six strings are stretched tight along the guitar. The thick ones play low notes and the thin ones play high notes. Pluck one and it shakes too fast to see clearly.
• Tuning pegs. Each string winds around a peg. Turn the peg one way to tighten the string and raise its note. Turn it the other way to loosen the string and lower it.
• Nut. The nut is a small bar with six grooves. It holds the strings in place and marks one end of the part that can shake.
• Frets. Frets are thin metal bars across the neck. Press a string just behind a fret, and the fret becomes the new end of the string. Each fret closer to the body makes the note one step higher.
• Bridge. The other end of every string is held at the bridge. When a string shakes, it tugs on the bridge, and the bridge passes that shaking into the wooden top of the guitar.
• Soundboard. The top of the guitar is a thin sheet of wood called the soundboard. The bridge makes it shake, and because it is so wide it pushes much more air than a skinny string can.
• Sound hole. The body is a hollow box full of air. That air shakes along with the wood, and the round hole lets its sound out. It makes the low notes fuller.

Pluck the string. Then change one thing at a time: press a fret to shorten it, turn the peg to tighten it, or pick a thicker string. Watch the slow-motion view and listen.

Experiment: You press the string down at a fret, so the shaking part is shorter. What happens to the note?

1. Pluck the open string and listen.
2. Tap the neck near the body to press a fret there. Pluck again.
3. Now try the peg (tighter and looser), and a thicker or thinner string.

What we found: A shorter shaking part swings faster, so the note is higher. Tightening the string also makes it faster and higher. A thicker, heavier string is slower and lower. Players use all three: thick and thin strings, pegs for tuning and frets for playing.

Turn on JavaScript to try it yourself.

Listen to the target note and find it on the note line. Use the string, the frets and the peg to match it, then check. Match four notes.

When you pluck a guitar string, you pull it to one side and let go. The string is stretched tight, so it springs back, flies past the middle and swings out the other way. It does this again and again, very fast. This shaking is called vibration. The string pushes the air, and the air carries the sound to your ears.

How high or low a note sounds is called its pitch. Pitch depends on how fast the string shakes. Fast shaking gives a high note. Slow shaking gives a low note. The lowest guitar string shakes about 82 times every second. The highest one shakes about 330 times every second.

Three things change how fast a string shakes. A shorter string shakes faster, which is why pressing a fret raises the note. A tighter string shakes faster, which is why turning a peg tunes it. A thinner, lighter string shakes faster, which is why a guitar has thick strings for low notes and thin strings for high ones.

A string by itself is very quiet, because it is too thin to push much air. The guitar's bridge passes the shaking to the thin wooden top, and the hollow body joins in. Our ruler comparison only goes so far: a ruler is stiff and is held at one end, but a string is floppy, is held at both ends and needs to be pulled tight before it can sing.

Key words

Vibration

A fast shaking back and forth.

Pitch

How high or low a note sounds.

Frequency

How many times something shakes each second.

Tension

How tightly a string is pulled.

Fret

A thin metal bar across the neck. Pressing a string behind it shortens the part that can vibrate.

Octave

A jump to the same note, but higher. Halving the string's length raises a note by one octave.

Soundboard

The thin wooden top of the guitar. It vibrates with the strings and makes the sound louder.

Check your thinking

1. Which string makes the highest note?

   Show the answer

   A short, thin, tight string. Shorter, thinner and tighter all make a string shake faster, and faster shaking means a higher note.

2. Why does pressing a string against a fret make the note higher?

   Show the answer

   The part that can shake is shorter, so it shakes faster. Only the part between the fret and the bridge can vibrate. A shorter piece swings back and forth more quickly.

3. A guitar string sounds too low. How does the player fix it?

   Show the answer

   Turn the tuning peg to tighten the string. A tighter string snaps back faster, so it shakes faster and sounds higher. Loosening it or using a thicker string would lower the note.

4. Why are the low strings on a guitar thicker than the high strings?

   Show the answer

   Thick strings are heavier, so they shake more slowly. A heavy string takes longer to swing back and forth. Slow shaking makes a low note.

5. A string stretched between two nails is very quiet. Why is a guitar so much louder?

   Show the answer

   The string shakes the thin wooden top, which pushes much more air. A thin string slips through the air. The wide soundboard pushes a lot of air at once, so the sound is louder.