Duration: 13:05 · 1080p Stream
Master video playlist mapped. Ready for batch offline download to media/videos/diatonic-harmony-mapping-triads-and-seventh-chords-across-the-fretboard.mp4.
Originally published November 8, 2025
In this video, I demonstrate how to map diatonic triads across the entire fretboard. With a small set of simple transformations, you can take any three-string triad shape and convert it into every other three-string triad shape in the key, on any string set. It's a really powerful toolkit for understanding the fretboard.
On a side note, for those who are interested in some of the behind-the-scenes workings...
...this is my first video where almost all of the animations were generated purely in Python code, without using Keynote at all. There are still some limitations to what I can achieve this way, but it makes creating this style of video simpler, allowing me to produce content like this more efficiently.
What follows is the written lesson — the full contents of the PDF handout, so you can read it here or download it above.
For guitarists, understanding diatonic harmony isn’t just about memorizing theory—it’s one of the most effective frameworks for learning and using triad and seventh-chord shapes across the fretboard. In this lesson, we’ll turn that theory into something you can see, hear, and play.
Diatonic is a music theory term that means that “all the notes come from the same musical key” (i.e., they all come from a single major scale). Diatonic chords are made by playing a subset of notes from that major scale at the same time. Diatonic harmony means that all of the chords in the music are derived from the same scale.
The most commonly used diatonic chords are triads, which are chords with three distinct notes. The most widely used diatonic triads are created by starting on a note of the major scale, which we’ll call the root (this chord root is not to be confused with the root of the scale). We skip over the following note in the scale (the second note) and add the third note to the chord. We then skip over the fourth note and add the fifth. Therefore, every triad constructed this way has a root, a third, and a fifth.
Because the major scale consists entirely of whole-step and half-step intervals, if you choose any consecutive sequence of three notes from inside the scale, the first and third notes will be separated by either three or four semitones—a minor or major third interval.
Depending on which note of the original major scale we start on, we get one of three different types of triads:
In the key of C major, where the scale notes are C, D, E, F, G, A, and B, you have this sequence of triads:
C, Dm, Em, F, G, Am, and B°
In Nashville notation, we would label these chords:
1, 2-, 3-, 4, 5, 6-, 7°
If we extend each of these chords by skipping the sixth note and adding the seventh, we get seventh chords. Depending on which note of the original major scale we start on, we get one of four different flavors:
In the key of C major, you have this sequence:
Cmaj7, Dm7, Em7, Fmaj7, G7, Am7, Bm7♭5
💡Note: The same pattern of chords holds for all of the major scale modes. The result for each mode is simply a rotation of the sequence from the major scale. For example, D Dorian starts on the 2- chord of C major, E Phrygian begins on the 3- chord, and so on.
Here’s a summary of what we’ve covered so far (this is worth memorizing):
| Scale degree | Triad type | 7th chord type |
|---|---|---|
| 1 | Major | maj7 |
| 2 | Minor | m7 |
| 3 | Minor | m7 |
| 4 | Major | maj7 |
| 5 | Major | 7 |
| 6 | Minor | m7 |
| 7 | Diminished | m7♭5 |
Let’s start connecting this theory to something you can see.
First, it’s helpful to visualize the major scale on one string. This is one octave of the F major scale on the D string, with each note marked with its scale degree:
If we want to build a diatonic triad on each note of the scale, we need three different shapes for the three types of diatonic triads. Here are the root-position triad shapes for the D-G-B string set:
Notice that you create a minor triad shape by moving the 3rd of the major triad down one fret, and you can make a diminished triad by also moving the 5th down one fret. I recommend memorizing the major triad shape and learning how to create the other two by manipulating the intervals. Doing this keeps your visualization focused on the root and reinforces your understanding.
We can build out the scale in harmony by placing the major shape on the 1st, 4th, and 5th scale degrees, the minor shape on the 2nd, 3rd, and 6th, and the diminished on the 7th. If we build out starting from the F major scale on the D string, these are the diatonic chords in the key of F on the D-G-B string set:
Practice this: It’s well worth practicing your triad fingerings by playing up and down a harmonized scale like this. The key is to visualize the major scale on one string (in this case, the D string) and to build the appropriate triad around each scale degree. Try to do this without referring to the tablature. It is beneficial to reconstruct it from memory. Finally, don’t be afraid to extend the scale both up and down to make use of the entire fretboard.
2.1 Three Inversions for Every Triad
Each triad type (major, minor, and diminished) has three inversions available on every string set:
These inversions are what make it possible to play smooth, connected chord changes in a small area of the fretboard without large jumps. Voice leading is the art of playing sequential chords so that each note (or voice) only changes by a small number of frets for each chord change.
Here are the first-inversion shapes on the D-G-B string set:
(Again, and for all future examples, I recommend memorizing the major triad shape and deriving the others when you practice. Eventually, they will all be committed to memory, but learning them this way will reinforce their relationships.)
To use these, we would visualize a major scale on the B string (i.e., where the root is) and build the appropriate shape around each scale degree. For example, here is the D major scale harmonized on the D-G-B string set (I have changed key only to keep the demonstration inside a similar range of the fretboard):
And here is the harmonized A major scale. To play this, visualize the major scale on the G string and build the appropriate triads around each scale degree:
At one level, that’s all diatonic harmony really is—a sequenced loop of major, minor, and diminished triads that moves through the scale.
2.2 Moving Between String Sets
These shapes are movable to any set of three adjacent strings (E–A–D, A–D–G, G–B–E). The fingerings remain similar, but you’ll need to make a slight adjustment whenever a part of a shape moves across the warp between the G and B string. As you shift to the next string set, any note that moves from the G to the B string is shifted one fret toward the bridge, and any note that moves from the B to the G string is shifted one fret toward the nut.
For reference, here are the major triad shapes for all three inversions on each string set (for all of these, you can lower the 3rd in any shape to make it minor and then lower the 5th to make it diminished):
Once you understand these small adjustments, you will be able to play the full harmonized scale on any three-string set and in any inversion. It’s only necessary to memorize the three inversions of the major triad on one string set (I suggest D-G-B), and every other triad shape is easily derived from that. Eventually, you will internalize all of the shapes, but there’s no need to explicitly memorize them as separate chords right away. Once again, it’s more useful in the long run to understand and internalize how they relate to each other.
Once you’re comfortable with triads, it’s natural to extend them into four-note seventh chords by stacking one more third on top (1–3–5–7).
Recall that each seventh chord type has a distinct “fingerprint”:
The most significant difference compared to triads is that many root-position seventh chords (and their standard music theory inversions) are not practical to play on guitar. In the voicings guitar players typically use, the notes are usually shuffled around a bit.
3.1 Root-Position 7th Chords on A–D–G–B Strings
We’ll start on the D-G-B-E string set and place the root on the D string. These are all commonly used voicings:
Notice that we can transform a maj7 chord to a 7 chord by lowering the 7th by one fret. We can transform a 7 chord to a m7 chord by lowering the 3rd by one fret. And we can transform a m7 chord into a m7♭5 by lowering the 5th. I recommend memorizing the dominant 7 chord shapes, since they are used most often, and practicing deriving the other shapes by shifting notes as needed.
Again, we can harmonize the full major scale by visualizing a scale on the D string and building the appropriate chord voicing around each scale degree. Here is the F major scale harmonized in this way:
Playing through these in order yields a rich, jazzy version of the harmonized major scale.
If we shift these voicings down a string set (minding the warp), we can play chords rooted on the A string (again, these are all commonly used voicings):
And here is the corresponding harmonized C major scale:
And the corresponding harmonized G major scale:
3.2 Common Inversions
Every 7th chord also has three additional inversions. These are often named by which note is in the bass (using slash notation), but for visualization purposes (and to use them for improvisation), it’s best to learn them by which string has the root.
Here are the inversions with the root on the high E string (again, these are all widely used voicings):
Notice that the top three strings are all triad shapes you already know.
And the corresponding G major harmonized scale:
And the corresponding C major harmonized scale:
And finally, here are the inversions with the root on the G string (again, all are usable):
Notice that the bottom three strings are all triad shapes you already know.
And the corresponding harmonized A major scale:
Again, note that you don’t have to memorize all of these shapes right away. During practice, there is a lot of value in reconstructing these voicings using your understanding of chord construction and working up and down the scale.
It’s a good idea to spend some time practicing harmonizing major scales in triads and seventh chords. I recommend working with triads until you feel you know them well. Then, move on to seventh chords.
Here’s how to practice them:
With 12 keys, 6 possible focal strings, and 1-3 possible string sets for triads and another 1-3 for seventh chords, this yields 864 possible exercises. Choose one or two variations each day and practice them. Begin with triads and common guitar keys (B, E, A, D, G, C). Start by focusing on the higher strings— those voicings are gold for rhythm guitar. If your focal string belongs to more than one string set, practice each possible string set. When you feel confident with triads, move on to seventh chords. Challenge yourself by playing the chords “out of order” by skipping scale degrees and moving around the scale less predictably.
Whenever you practice diatonic harmony in this way, listen carefully to what you are playing. Your ears should tell you immediately if you make a mistake, especially if you establish the sound of the key first by playing the scale on its own. Once the tonality is established, our ears are very good at picking out notes that don’t fit the key, and if you’re executing these exercises perfectly, that should never happen.
The exercises in this lesson are mostly academic skill-builders. They are great for reinforcing your knowledge of triad and seventh-chord voicings, as well as your understanding of diatonic harmony, but they aren’t very musical.
Using this knowledge to create music is a massive topic, and this lesson is already quite long, so I’m going to give you two hints rather than more exercises or exposition:
Both of those seed ideas are worth complete lessons on their own, so stay tuned for that!
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