Introduction to music theory Octaves | music theory for guitarists

Previous articles in this series – strongly recommended to read this first!

Intro to music theory (the 12 notes)

What is an Octave?

When we play notes on a string moving up one fret at a time, the notes are ascending in pitch. Each note is higher than the last.

One Octave Higher

If you play any open string and then that same string as the 12^th fret, you will notice that they sound the same but one is ‘higher’. So one has higher pitch but still they sound very much in tune with each other.

Example: Play that thickest string (E) open and at the 12^th fret – they are both “E” but the 12^th fret is one octave higher.

Two Octaves Higher

Play the thickest string on your guitar and then the thinnest string on your guitar, these are also both E notes but the thin string is two octaves higher. It should be obvious that this 6^th string (thickest) has a lower pitch and the first string (thinnest) has a higher pitch. It should be clear to your ear that they are both the same pitch class (i.e. same note higher/lower)

If this isn’t clear, play both together and hear that they are in unison (i.e. not different to one another)

The Importance of the Octave

Music as a guitarist could get quite boring if we were only able to play in one octave.

The guitar is an instrument that spans four octaves and this enables us to play over a great range. You could play a bass line with the low E and A strings or go really far up to the 12th fret and beyond to do a Jimi Hendrix type lead guitar solo.

In the context of this guide to guitar theory, understanding octaves helps us to:

Identify a note on a given fret/string
Identify (say) all the E notes on the guitar neck
Learn scales and chords higher up the neck
Tune our guitar
And much more

All the E Notes

One immediate application of octaves is identifying all the instances of a certain note on the guitar fretboard.

Below is a map of all E notes on the guitar fretboard.

Next, I’m going to show you how to use octaves to figure out these notes yourself.

Here are a few rules you can apply.

Rule 1: 12 Frets Higher

Any note 12 frets higher on the same string is an octave higher

We know that we have 2 strings that are both E (thinnest and thickest strings).

If we play those strings at the 12th fret, those notes will also be E

Thus,

The 2 blue notes are an octave apart
The 2 red notes are an octave apart

TIP: All the following note pairs are an octave apart

Playing a string open (not fretted) and then at the 12^th fret

Playing a string at the 1^st fret and 13^th fret

Playing a string at the 2^nd fret and 14^th fret.

RULE 2: Fret 7 & the String above

Play any string at the 7^th fret and then play the string above it (i.e. one string closer to your face). These 2 notes are an octave apart.

One exception – you need the 8^th fret on the B string so the (G) string above is an octave below. This is shown in red below

RULE 3: Down & Across

We have a pair of rules:

For the 2 low strings (E or A) -> down 2 strings and up the neck 2 frets is an octave higher
For the 2 middle strings (D or G) -> down 2 strings and up the neck 3 frets is an octave higher

Let’s take a look at the first rule playing

the E string at 5th fret (A note)
the open A string (also an A note)

The red lines show how I go down 2 strings (towards my toes) and up the neck 2 frets. All four of these notes are A notes

TIP: Cross-check your octaves from time to time

In Chapter 1 we saw that G  G sharp  A so we can cross-check that the G string at the 2^nd fret is an A note.

If we take the A notes on the middle strings we can go down and across 3  this generates two more A notes

We have now actually calculated all the A notes on the fretboard (once we add in the A string at the 12^th fret)

E Example

Let’s take a look at how to calculate all the E notes on the fretboard.

We have 2 open E strings.

Rule 1: 12 notes higher

And we know that the 12^th fret of those E strings will also be E notes.

Here the blue notes are an octave apart and the red notes are an octave apart (all E notes)

Rule 2: Fret 7 and the open string above

Here we can just take the low E string and we know that the 7^th fret of the string below is an octave higher. In our case, the green note below is the 7^th fret of the A string (the string below).

Rule 3: Down and Across

For our E notes that are located on E and A strings, we can move down 2 and across 2 to get more E notes (the red lines below)

For the E notes on our middle strings (D and G strings), we can move down 2 strings and up 3 frets to get more E notes an octave higher (the purple notes below)

Summary

This chapter helped to explain what happens after we run through our cycle of 12 notes.

A note 12 frets higher is an octave higher.
The relationship between notes is identical but the higher octave notes are higher in pitch.
Being able to identify all the places on the fretboard where a given note occurs really helps us to unlock the fretboard. We learned a few simple rules for how to identify notes an octave higher and lower.