Pitch
How high or low a sound is.
Paused by your reduced-motion setting
Find Your PitchSeason 1Lesson 01
If 440 Hz shakes the air twice as fast as 220 Hz, why do musicians call them the same note?
By the end you'll know what a note really is, why notes come back an octave higher, and how to read names like A4 and C4.
This lesson is about sound. Tap to turn it on: nothing plays until you press a play button.
TaviHa! Same note.
MercIs it? Mine shook the air 220 times a second. Yours shook it 440.
Predict before you listen
Two different notes, or the same one?
Choose an answer to unlock the play buttons.
Your guessOne after the other, 440 sounds higher. Played together, they melt into one sound. Alike enough that music gives them one name: by the end of this lesson you'll know why.
Three words you'll meet before the first step
Pitch, hertz and the octave
Hertz Hz
Swings per second.
Octave
The jump to twice as many swings per second: the same note, one level higher.
Six steps, one object: a line, then a spiral, then a piano
What is a note?
Step 1 of 6
Fig. 1 The plucked string
Swings0
Time0.0s
Speed220per s
Tap the string to pluck it
Fig. 2 The frequency dial
Frequency220Hz
One swing every4.55ms
Fig. 3 How far and how fast
Loudness50%
Pitch220Hz
Hold a slider to hear it
Fig. 4 Two waves, one fit
Ratio2.00×
Orange440Hz
Blue220Hz
Gold marks where the peaks meet
Octave ladder
Fig. 5 The pitch spiral
Last note—
Drag to turn · tap a bead to hear it
A spiral of 37 beads from A2 to A5, three turns. Every A sits on the same side, and a seam marks each C, where the octave number goes up. Drag to turn it, or turn it a bead at a time with Turn left and Turn right; tap a bead to hear it. With the keyboard, the arrow keys pick a note, Enter or Space plays it, and Shift with Left or Right turns the spiral. Unrolled, the same keys walk the piano.
A3 to A4
Step 1 of 6
A note is something shaking
Every note you've ever heard starts with something shaking: a guitar string, a speaker cone, the vocal folds in your throat. Pluck a string and it swings back and forth, pushing on the air. Each push travels outward as a wave, all the way to your ear.
TryPluck the string. Then turn on slow motion.
NoticeSlowed 220 times, the string swings once a second: there and back is one swing.
Step 2 of 6
Count the swings
Count the swings in one second and you have the note's frequency. We measure it in hertz: swings per second. This string swings 220 times a second, so its note is 220 Hz.
TryDrag the dial from 110 to 880 Hz.
NoticeFaster swings make a higher note, and the bead climbs. Your ear hears speed as height.
Step 3 of 6
Loud is not high
TryMove the “how far” slider, then the “how fast” one.
NoticeOnly “how fast” moves the bead. That's why MercuryPitch draws your voice as a line that climbs when you go higher, soft or loud.
Step 4 of 6
Twice as fast
Back to the puzzle. 440 is exactly twice 220. Lay the two waves on top of each other: every other peak of the fast one lands right on a peak of the slow one, again and again, forever. Two for one: the simplest fit there is. That jump is called an octave.
TryPress Play both, then slide the ratio from 1 to 3.
NoticeAt exactly 2 the waves meet on every slow peak, two for one. At 1.26 (277 Hz, a different note) they drift in and out of step. At 3 they meet again, three for one, but that's a different note too. Of all the fits, two for one is the simplest: that's the octave.
The octave keeps going: 110, 220, 440, 880. Each doubling sounds like the same size of jump, even though the gap in hertz doubles every time. From 110 to 220 is 110 Hz; from 440 to 880 is 440 Hz. Your ear hears multiplying, not adding.
Step 5 of 6
Pitch is a spiral
So pitch isn't really a straight line. It's more like a spiral: go up an octave and you come back round, right above where you started. Musicians name the notes with seven letters, A B C D E F G, and then the pattern repeats.
TryTurn the spiral, and tap any bead to hear it.
NoticeEvery A sits on the same side, one turn apart. Between the letters there are five more notes without a letter of their own. Twelve in all: that's Lesson 2.
Step 6 of 6
Names and numbers
The number tells you which turn of the spiral a note is on. It goes up at C, not at A, so B3 is followed by C4. The A that orchestras tune to is A4, 440 Hz, and middle C on a piano is C4. A3 and A4 share a letter because A4 swings exactly twice as fast: they're an octave apart, same spot on the spiral, one turn higher. Unroll the spiral and you get the piano: the same seven letters, octave after octave.
TryUnroll the spiral into a keyboard; tap A3, then A4.
NoticeThey sit seven white keys apart and still sound like the same note.
Cadenza: your solo, and any octave counts
Sing it
When two people sing the same tune, they're often an octave apart, and it still sounds like one tune. So when you match a note, an octave up or down counts.
Your turn: play Merc's A. Hum it back, wherever it feels easy.
Humming along here is just for you: nothing listens and nothing is scored.
Keep it gentle. Never push, and stop if anything feels uncomfortable.
A3 · 220 HzReady when you are
Practise in MercuryPitch
Voice Mirror
Want a score? Try MercuryPitch's Voice Mirror. It finds your comfortable range, then plays five notes for you to sing back on “ooh”, and counts a match in any octave. Free, no account.
mercurypitch.com/mirrorRipresa: the theme comes back, from memory
Quick check
Tap an answer one try each, then the reason
0of 4
Coda: the closing bars
Three lines to keep
- A note is something shaking; its frequency is swings per second, in hertz.
- Faster is higher; bigger is louder.
- Double the frequency and the same note comes back an octave higher, so pitch is a spiral, and the piano is that spiral unrolled.
One-sentence challengeExplain to a friend, in one sentence, why a man and a woman singing “the same” tune can be an octave apart.
The same lesson, as a film: 5:35, captions on
Watch the episode
Chapters tap to jump
Read the transcriptfrom the captions
Season 1, fourteen lessons and a trailer: theory and voice, alternating
The season, mapped
Each lesson's closing question opens the next. Pick a lesson to light up the path of lessons it builds on.