What Are Octaves In Music? A Music Theory Guide

By Jade Bultitude
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You may have heard the term octaves in music lessons and wondered exactly what is means. In this post we will explore what an octave is, how to play it, where you can hear it featured in music and how to use it in music theory.

What is An Octave?

To really understand what an octave is we must first explore what an interval is.

What is an Interval?

An interval put simply is the distance between two musical notes or pitches. These two pitches could be one note apart, two notes apart, three notes apart and beyond. Octaves in music is simply one example of an interval. There are twelve intervals in music, thirteen if you consider the unison interval which is two notes of exactly the same pitch played simultaneously. If you want to know more, check out our complete guide to intervals.

How Many Notes In An Octave?

As we have seen, an octave is an example of a musical interval. Remember an interval is simply the distance between two musical notes. An octave has eight notes in its interval.

c major in treble clef

As you can see above we have an octave interval from middle C to C on the stave.

C D E F G A B C

What we have written above is the C major scale. As you can see the first and last notes have the same note name but the higher note is one octave higher! You can continue in this way and create multiple octaves above the starting note of C. Or of course, if you go the other way you could create multiple octave lower than the starting note.

Think about the start of the word OCTave. We see this in other places within language as well. How many legs does an Octopus have? How many sides does an Octagon have?

An octave in music will be two notes played either one after the other or at the same time which are eight letters apart. These two notes will have the same letter name but one will be lower than the other. They are two notes with the same letter name/pitch but that have a different frequency.

How many Semitones in an octave?

You can also look at the interval of an octave in terms of semitones (half step). An octave spans 12 semitones. If you look at this on the piano keyboard you can see that this includes all white keys and all black keys.

twelve tones on a keyboard

What does an Octave Sound like?

frequency of an octave

A pitch that is one octave higher than a lower note will have double its frequency. Frequency refers to the sound wave vibrations. For example, if our middle C vibrates at 440 hertz (cycles per second) as is most common in the UK, then the next C an octave higher will vibrate at 880 hertz. The C an octave lower will vibrate at 220 hertz.

How many octaves are there?

Theoretically are infinite number of octaves because we can keep doubling or halving our frequency to find higher or lower notes.

Examples of Octaves in Music

Octaves in music can be found in many different genres, including in classical music, jazz music and rock music to name but a few!

‘East Wes’ – Eric Johnson

This piece was inspired by Wes Montgomery, the famous jazz guitarist. The main riff contains a series of octaves strummed with the thumb.

east wes by eric johnson octaves

‘Somewhere over the Rainbow’ – The Wizard of Oz

The first interval of somewhere over the rainbow features an octave from C to C.

somewhere over the rainbow ocave

Mozart’s 29th symphony- Opening Theme

The opening of this symphony featured a descending octave of A to A.

Mozart 29th Symphony Octave motif

Ear Training and Intervals

To develop as a musician you’ll want to be able to recognise intervals by ear. This is where ear training comes in, as the more you practice, the better your’ll get.

My recommendation for this is Tonegym as they have a comprehensive and fun program for training your ears. It’s what has gotten the best results with for my own students.

In the ‘tools’ section of their site, Tonegym even have an interval memorizer that allows you to learn every type of interval.

For an in-depth look at ear training, here’s my full review of Tonegym.

departurer opt tonegym

How to Play Octaves on the Piano

On a standard piano there are 88 keys with the lowest note being an A. If you count up in octaves on a piano keyboard from this A, you will find that there are eight A’s all an octave apart, meaning that the piano keyboard has seven octaves. If you start from a different pitch on the piano then there may be less!

piano with 88 kays and 7 octaves facts

As you can see on the piano keyboard, we have highlighted all the notes an octave apart. Each pitch highlighted has the same note name. A full-sized piano has a range of just over 7 octaves.

piano keyboard with octaves labelled

octaves on a guitar?

A 24 fret guitar has a range of four octaves with its lowest note being the E below middle C.

There are a number of ways to play octaves on guitar. The four main shapes are below. Each involves muting the middle string of the shape so that only the two octave notes sound.

You can move each shape up and down the neck to create different octaves.

tab for playing octaves on guitar

Understanding octaves is extremely important within music theory. Remember an octave is two notes that share the same note name with these two notes separated by eight different notes.

How are Octaves Labelled

Octaves in music are give names with the usual range being from C0 to C9. If we take the note B4 this would be the B above middle C. (Middle C is C4). This gives us a handy way to refer to the same note but in different octaves.

C0 to C9 on the stave

In sheet music you may see ‘8va’ with a dotted bracket. This means that the we should play the notes in the bracket one octave higher than written. Similarly we can use the below the notes to indicate ‘one octave lower than written’. You might also see 8ba for ‘one octave lower’.

octaves labelled using musical notation

What’s Next…?

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AUTHOR
Jade is an experienced musician and teacher as well as being the founder of Music Theory Foundations. She has been helping people learn music theory for more than 10 years from pre school children all the way to degree level studies.