Learning how to find intervals quickly on guitar is important for generally playing, improvising, and enjoying the instrument. I’ve gone through how to find notes on the guitar, which should give you some understanding of the fretboard. Continuing from generally finding notes, being able to find intervals is also important. Let’s start with finding octaves.
All of the below is, of course, assuming standard guitar tuning. None of this will work with other tunings on the guitar.
What Is An Octave?
An octave is the note 12 semitones higher than the root note. It’s the same note, just twice the frequency of the root. There are only 11 notes in music before they repeat themselves (just higher), so at the 12th semitone, you’re back to the root, just higher. That’s an octave.
Knowing where your octaves are is just another step to quickly finding notes within the key you’re playing it. Knowing your guitar scales is important of course, but if you combine this with a deeper understanding of musical intervals on guitar, you’ll never get lost.
Octaves are found in three basic ways/shapes on the guitar. I’m calling these the adjacent string/12th fret octaves, forward octave, and backward octave. I’m sure other people call them something else. It’s just the names for the shapes I just made up.
What Does An Octave Sound Like?
If you want to be able to do an octave in your head so you can know what it sounds like when you’re not at the guitar, the first two notes of Somewhere Over The Rainbow are a good reference. Just sing that song to yourself and you have your octave right there.
Adjacent String and 12th Fret Octaves On Guitar
Since the octave occurs 12 semitones (frets) above the root, you’re going to find the octave for a given note 12 frets above it. On the open strings, this is the 12th fret.
You’ll also find the octave on the adjacent string 7 frets up (8 frets if the adjacent string is the B string because of standard tuning). So on open strings, this is obviously the 7th fret. If you’re not on an open string, just add 7 frets.
Forward Octaves On Guitar
I call this the “forward octave” because the octave is occurring in front of the root. These are really handy octave because you can play them in the same position you’re already in. You’re just going two string up and 2 frets forward (or 3 frets when dealing with the B string).
The diagram here shows where the octaves across the strings in different colours. That is to say, each colour is a different octave (different notes). Assuming you’re familiar with your open guitar chords as well as their corresponding barre chord shapes, you should be able to kind of see the E shape, A shape, D shape, and C shape in these octaves. If you don’t see how these are like the chord shapes, fret the chords and find the octaves. You’ll see then.
Backward Octaves On Guitar
I’m calling these octave shapes backward octaves because the octave is behind the root note (in relation to the guitar neck). These octaves also don’t require you to change position, but do rely on you playing the root with your third or fourth finger.
Like the forward octaves, I’ve colour coded everything across the strings so you can find the octave regardless of where you’re playing. These octaves should remind you of the G shape, C shape, and E shape chords.
And That’s Octaves On The Guitar
I find the hardest one to remember is the backward octave, but your milage may vary.
To practice these intervals, include them when you’re practicing your scales. Go through your scales, have a jam, then throw in a few octave jumps. You’ll have them in no time.