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.
Definition of 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. An octave 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 about intervals then make sure to check out my blog post here.
How Many Notes Are In A 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.
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.
The 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?
There are infinite number of octaves so this question should really relate to specific instruments. Best place to start is the piano!
Octaves On A 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!
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.
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.
Examples of Octaves in Music
Octaves can be found in many different genres of music, including in classical music, jazz music and rock music to name but a few!
Eric Johnson’s ‘East Wes’ – This piece was inspired by Wes Montgomery, the famous jazz guitarist. The main riff contains a series of octaves strummed with the thumb.
The first interval of somewhere over the rainbow
Mozarts 29th symphony opening theme. Downward octave leap as main motif.
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.
- Learn more about other intervals with our complete guide.