In this guide
An octave is the interval between two pitches where the higher fundamental frequency is twice the lower. In twelve-tone equal temperament, it spans 12 semitones; notes an octave apart usually share a letter name but sit in different registers.
An octave in music is the interval between two pitches when the higher note has twice the fundamental frequency of the lower note. For example, a 220 Hz A and a 440 Hz A are an octave apart. They have the same note name but sound in different registers.
In the familiar twelve-tone equal-tempered system, an octave spans 12 semitones, also called half steps. On a piano, moving from one C to the next higher C gives an octave; moving to the next lower C gives a descending octave.
Why are notes an octave apart given the same name?
Notes an octave apart have a close pitch relationship, so musicians often treat them as different registers of the same note class. They are not the same pitch: one is higher than the other. Their fundamental frequencies form a 2:1 ratio, as explained in the Open University's lesson on frequency and note identity.
| Example pitch | Frequency | Relationship |
|---|---|---|
| A3 | 220 Hz | One octave below A4. |
| A4 | 440 Hz | Twice A3's frequency in this standard tuning example. |
| A5 | 880 Hz | Twice A4's frequency and two octaves above A3. |
The number after the note name identifies its octave in this notation. The examples use A4 = 440 Hz; musicians may use other tuning references. Doubling frequency raises a pitch by an octave, while halving it lowers the pitch by an octave.
How to find an octave on a piano
- Find any C. On a standard keyboard, C is the white key immediately to the left of a group of two black keys.
- Move right to the next C. The two Cs form an ascending octave.
- Count every adjacent key from the first C to the next, including black keys. There are 12 semitone movements; do not count the starting key as the first movement.
- Play the two Cs separately, then together. Notice their similar note identity and different heights.
There are eight letter-name positions when counting C–D–E–F–G–A–B–C inclusively, which is why the interval is called an octave. The seven distinct letter names and 12 semitone movements are different ways of counting; neither requires ignoring the black keys.
Octaves, scales and intervals
An octave is one specific musical interval. A scale is an ordered collection of pitches and is often demonstrated from one note to the note an octave above. For example, C major can be shown as C–D–E–F–G–A–B–C. The first and last C are an octave apart; the scale also contains the notes between them. See what a scale in music is.
Different instruments and singers can perform the same melody in different octaves. A bass and a higher voice may use corresponding note names while sounding in different registers. The sound also depends on timbre and performance; an octave relationship alone does not make the recordings identical.
Try an octave listening exercise
- Play a comfortable note, such as A3, then the next A above it. Listen for the upward jump.
- Play the lower A again, followed by the A below it if your instrument and hearing range allow. That is an octave downward.
- Play a short three-note phrase and repeat the same note relationships an octave higher. Compare the shape of the phrase and its register.
- If singing, choose a comfortable range. Do not force the high or low note; use an instrument or recording if it falls outside your voice.
Can you shift an audio recording by an octave?
In a semitone-based pitch shifter, +12 semitones is one octave up and −12 semitones is one octave down. Shifting a complete mix affects every audible source, not only the lead voice. Pitch processing can introduce artifacts or change timbre, especially with a large shift, so listen to the actual output.
The Saturalabs audio pitch changer can process a supported short local MP3 or WAV while attempting to preserve its tempo. Check its current input and output limits and compare the export with the original. To choose a smaller transposition for a singer, see how to change the key of a song.
Common questions
How many notes are in an octave?
In twelve-tone equal temperament there are 12 distinct pitch classes before the starting pitch class repeats. A seven-note major scale written from C to the next C displays eight note positions because C appears at both ends.
Is an octave higher twice as loud?
No. An octave concerns pitch and frequency, not loudness. Two notes an octave apart can be played at many different levels.
Does singing an octave higher change the melody?
The melody's pitch relationships can remain the same while its register changes. Whether a performer can sing it comfortably depends on their range and the arrangement.