The Note System
A musical note is a named pitch. Western notation uses seven letter names, A through G, while the common twelve-note system places five additional pitches between them. The names repeat at each octave because doubling frequency produces strong octave equivalence. Follow the interactive lesson below to learn more.
Find your first note
A note is a speed you can name.
What you just learned
- A note is a speed
A note is a speed
A note vibrates at a steady speed. The A above middle C vibrates 440 times a second.
A4 = 440 HzRead the full answer ↓ - Double it
Half or double, same letter
Halve or double the speed and your ear still hears an A. That distance is called an octave.
220 · 440 · 880 HzRead the full answer ↓ - Seven letters
Seven letters for the white keys
Inside one octave the white keys spell A to G, and then the letters start over.
C D E F G A BRead the full answer ↓ - Seven letters
One key, two names
The black key above C is C sharp counting up, and D flat counting down from D.
C♯ = D♭Read the full answer ↓ - Good to know
The number is the octave
Middle C is C4. The number goes up by one at every C, so B3 sits just below it.
B3 → C4 → C5Read the full answer ↓ - Try it
Find C without counting
C is the white key just left of every group of two black keys.
two black keys → CRead the full answer ↓
Where to go from here
Every part of the lesson, answered in full
Open any question to read the full answer.
What makes a sound a note?
A stable periodic sound usually gives the ear a clear pitch. A tuning tone at 440 cycles per second is labeled A4 when that reference standard is in use.
Real instrument notes are complex. They contain a fundamental, upper partials and an envelope that changes through time. The note name follows the pitch we hear, which is often related to the fundamental but is not always identical to the strongest measured frequency.
Why do note names repeat?
Double 440 Hz to 880 Hz and the result is another A, one octave higher. Halve it to 220 Hz and the result is an A one octave lower.
The notes differ in pitch height, yet share a strong pitch-class identity. Their harmonic patterns align closely, which helps the auditory system group them as versions of the same note name.
How do seven letters cover twelve pitches?
The letters A, B, C, D, E, F and G name the seven natural notes. Sharps and flats name the five common pitch positions between them.
| Move | Symbol | Example |
|---|---|---|
| raise by one half step | sharp | C becomes C-sharp |
| lower by one half step | flat | D becomes D-flat |
| cancel a sharp or flat | natural | F-sharp becomes F-natural |
On a piano, the natural notes are the white keys and the usual sharp or flat positions are the black keys. The black-key groups of two and three make the repeating pattern visible.
Why can one piano key have two names?
C-sharp and D-flat sound at the same pitch on an equal-tempered piano, but they are spelled differently. The notation tells you how the note functions.
A C-sharp often behaves as a raised C and may continue upward to D. A D-flat is a lowered D and may continue downward to C. The key pressed can be identical while the written route differs.
These are enharmonic spellings. More unusual spellings, such as B-sharp or F-flat, appear when the musical grammar requires every letter to keep its proper place in a scale or chord.
What do octave numbers mean?
Scientific pitch notation adds a number to identify register. Middle C is C4. The A above it is A4; the next C is C5.
The number changes at C, so B3 sits directly below C4. This convention prevents instructions such as "play C" from leaving eight possible piano keys unspecified.
Find any note on a keyboard
Find C. Locate a group of two black keys. C is the white key immediately to its left.
Continue the letters. Move right through C, D, E, then F, G, A, B. The sequence restarts at C.
Name black keys from context. The black key between C and D can be C-sharp or D-flat. Choose the spelling the music requires.
Is A always 440 Hz?
A4 = 440 Hz is a widely used reference, but ensembles can agree on another value such as 442 Hz. The note relationships remain the same when every pitch shifts together.
Tuning reference answers "where does A sit?" Temperament answers "how are the other notes spaced?" Those are separate choices.
Build the map yourself
- 1. Find every C - use the two-black-key pattern instead of counting.
- 2. Find A4 - locate the A above middle C and play 440 Hz.
- 3. Move an octave - compare A3, A4 and A5.
- 4. Name the black keys - say both common enharmonic names.
- 5. Write three registers - label C3, C4 and C5 before playing them.