Interval · P8 · 12 half steps
The octave
A octave is 12 half steps wide: C to C. Somewhere over the Rainbow.
- Half steps12
- Letter names8
- From CC–C
- Inverts tounison
The octave on the staff
An interval’s number counts letter names from the bottom note to the top, both included: C, D, E, F, G, A, B, C is eight, an octave. On the staff, one note is on a line and the other in a space: from a line, it lands in the fourth space up; from a space, on the fourth line up.
The number alone doesn’t make it a octave: C to C is always an octave, but C to C♯ an octave up is an augmented octave.
Each example below plays the two notes one after the other (a melodic interval), then together (a harmonic interval).
On the piano
Count half steps: every key, black or white, is one half step from the next. From middle C, the octave is the next C up, C.
Most adult hands stretch an octave with thumb and little finger. Find it by letter: the next key with the same name, seven white keys up.
On the white keys alone, the octaves are C–C, D–D, E–E, F–F, G–G, A–A and B–B: every white key.
How a octave sounds
An octave sounds like the same note, only higher or lower: the two notes blend so completely that they share a name. Played together, octaves sound full and strong, which is why left hands double bass lines in octaves.
In harmony, it’s a perfect consonance: the two notes blend almost into one.
Tunes that start with it
- “Over the Rainbow” starts with an octave up: “Some-where”.
Hum the tune’s first two notes and you have the interval: a quick way to sing one before you play it.
Where you’ll meet it
An octave is eight letter names counting both ends (C up to the next C), and twelve half steps. The higher note vibrates exactly twice as fast. Left-hand octaves give bass lines weight, and right-hand octaves make a melody ring out above an accompaniment.
Turned upside down, with the bottom note moved up an octave, a octave becomes a octave again: 12 and 12 half steps make an octave.
To read it fast in real music, practise intervals the way you read words: as shapes. Level 18: right-hand intervals in the free sight-reading exercises has plenty of them.
Quiz: the octave
Ten questions: name the interval on the staff, among its neighbours, and play a octave above a written note on the piano below, a MIDI keyboard or your computer keys.
The quiz needs JavaScript.
A octave above every note
| From | A octave up |
|---|---|
| C | C |
| C♯ | C♯ |
| D | D |
| E♭ | E♭ |
| E | E |
| F | F |
| F♯ | F♯ |
| G | G |
| A♭ | A♭ |
| A | A |
| B♭ | B♭ |
| B | B |
Each one is spelt with the 8th letter up, which is why some need a sharp or flat that looks unusual, like C♯ up to C♯.
Questions
How many half steps are in a octave?
12 half steps, or 6 whole steps. Count every key, black and white, from the bottom note up to the top one: C to C is a octave.
What is a octave above C?
C. An octave keeps the letter name.
What is the inversion of a octave?
An octave turned upside down is a unison: the same note twice.
How do you recognise a octave on the staff?
One note is on a line and the other in a space: from a line, it lands in the fourth space up; from a space, on the fourth line up. That tells you the letter distance; then check the sharps, flats and key signature to tell perfect from augmented or diminished.
What song starts with a octave?
“Over the Rainbow” starts with an octave up: “Some-where”.
Hear every interval in real music
Pianomi, a free sight-reading app for piano, writes new pieces at your level and listens to your MIDI keyboard, so intervals become shapes you read without counting.