In our previous lesson, we saw that in the chromatic scale, we would start on a note, then 12 notes later, we'd be back on the same note. This actually applies to every string on a guitar:
If you listen carefully, you'll hear that for each open string note, its 12th-fret counterpart note sounds the "same", but higher. This is because after 12 half steps from an originating pitch, we end up at what's called an octave. An octave of a note is a note that sounds the "same", but is higher (or lower) in pitch.
From a science-based definition, an octave is a note that has its sound wave frequencies vibrating at a factor of two from the originating note. You can think of each note in music as having a sonic space on a frequency "timeline". To better visualize this, check out how these octaves for an A are laid out:
It's this frequency multiple that creates the characteristic of having the same tone but sounding higher/lower. Let's listen to octaves for a different note to see how they sound the same as well:
Hear how all these B's sound similar as well, but just higher/lower? Now, let's compare this set with another set of notes that aren't octaves:
These notes don't have frequencies that are apart by a factor of two (and thus aren't octaves), and it becomes pretty apparent when you listen to them. You can compare the distances between these notes with the distances in the octave examples above and actually visualize how this contributes to the sound differences as well.
Octaves are especially important because of how well they harmonize. Together, they create a pleasant and enjoyable sound:
But here, the last set of notes harmonize to create an ugly, spooky sort of sound:
Now let's listen to some more notes on the guitar, using the 5th and 6th string as an example:
If you listen, you'll hear that the E on the 12th fret/6th string sounds higher than the A the open 5th string. Yet, this A sounds higher than the open note E on 6th string. This must mean that in terms of frequency, this A lies somewhere inbetween the two E's:
See how the A is actually inbetween the two E's? So, if we think about it, this means that going up the 6th string, we should run into that same A -- and we do! There's another A on the 5th fret/6th string. This A is actually the same exact note as the A on the open 5th string. They are in perfect unison (they are the same frequency):
This also applies to a pair of notes on the 5th/4th strings:
... and the 4th/3rd strings:
... the 3rd/2nd strings:
... and the 2nd/1st strings:
So, how can we use this concept of octaves and the chromatic scale to tune your guitar?
For every string except the 3rd string (G String), the note on the 5th fret is equal to the open string above it. On the 3rd string, it's the note on the 4th fret that's equal to the open string above it.
The reason why the 3rd string is different is actually to maximize the amount of chord voicings we can do on a guitar. If you were to hypothetically shift each note on the 3rd string up by one fret to be tuned like the other strings, we wouldn't be able to play any barre chords.
But anyway, if you're ever in a pinch and you know these note equivalencies across the fretboard, all you really need is to hear one string in order to tune your entire guitar. You can tune the rest of the strings by comparing the sound of the open strings to the sound of their equivalent notes like so:
1. Which one of these frequencies is not an octave of the others?
2. Which fret usually has a note equivalent to the open string adjacent to it?
3. Which string is the outlier string that doesn't apply to the principle above?
4. Which fret does the outlier string use instead?
In our next lesson, we'll go over root note patterns and how you can use them to locate any note on your fretboard.
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