The Map
Where the twelve came from
One plucked string already contains a chord. That is the whole origin story.
Take the guided lessonA string never plays one note
Pluck an open A string and it vibrates along its full length. It also vibrates in halves, in thirds, in quarters, all at the same time. Each of those adds a quieter, higher note on top.
That stack is called the overtone series, and it is the same for every string, every instrument, everywhere. Nobody designed it. It falls out of physics.
The notes hiding in one string
These are the first overtones of a low A, played one at a time. Every one of them is already sounding, quietly, whenever you play that open string.
Listen to what arrives and in what order. The octave comes first, then a fifth, then another octave, then a major third. Your ear has been hearing that stack under every note you have ever played.
The order they arrive in
Each overtone is a whole number multiple of the original frequency. The simpler the ratio, the more your ear treats the two notes as belonging together.
| Overtone | Note above A | Ratio | What your ear does with it |
|---|---|---|---|
| 1st | A, the note itself | 1:1 | This is the fundamental, the pitch you think you played |
| 2nd | A, an octave up | 2:1 | So consonant it barely registers as a second note |
| 3rd | E, a fifth above that | 3:2 | Strong and stable. This is the power chord interval |
| 4th | A, two octaves up | 4:1 | Another octave, reinforcing the root again |
| 5th | C sharp, a major third | 5:4 | Quieter. Adds colour rather than structure |
| 6th | E again, higher | 3:2 | The fifth returning, now in the upper register |
| 7th | Roughly G, but flat | 7:4 | Sits between two frets. No key on any piano plays it |
The first three rows are highlighted because they do most of the work. Almost everything in Grade 4 and Grade 5 traces back to them.
This is why some intervals sound stable
The first overtone to arrive after the octave is a fifth, and it is also the loudest. That is why a root and a fifth together sound solid rather than tense. You are reinforcing a note the string was already producing.
The major third shows up later and quieter, which fits how it behaves. It colours the chord rather than holding it up.
Build a scale by stacking those strong early relationships and keep going until the notes start repeating, and you land on twelve. That is the short version of an argument that took centuries to settle.
That seventh overtone is noticeably flat against anything on your fretboard. It sits in a crack between two frets, and that crack is roughly where blues singers and bent guitar notes live.
Match each overtone to what it gives you
Straight from the table. No listening required, just the relationships.
Tap something on the left, then tap what it pairs with.
Why a power chord survives distortion
Here is the practical payoff, and it is worth turning your volume down a little. Both of these are A chords played through a high gain amp.
Play both, then play them again in the other order.
The same chord, clean
None of this means the third is bad. Play those two chords on a clean amp and the triad is the richer, more expressive one.
It means gain is a filter on what harmony survives. That is why metal and hard rock lean on power chords and why the same riff sounds thin and empty played clean.
Why do power chords stay clear through heavy distortion when full major chords do not?
Which of these follow from the overtone series?
Takeaways
- One string already contains a stack of quieter notes called the overtone series.
- The octave and the fifth arrive first and loudest, which is why they sound stable.
- The major third arrives later and quieter, so it colours rather than supports.
- Gain amplifies that stack, so power chords hold together and driven triads do not.