Playing Diatonic Intervals All Over the Guitar Neck
Whether you’re composing, improvising, or refining your melodic vocabulary, visualizing intervals between two adjacent strings makes it easy to internalize both the sound and location of every interval.
In this post, we’ll walk through all diatonic intervals—2nds through octaves—using the C major scale as our foundation, while labeling chords using the John Mehegan system, which uses uppercase Roman numerals I through VII for all diatonic chords. Only non-diatonic chords are marked with additional symbols.
We’ll also introduce the idea of interval outliers: a way to simplify the process of memorizing interval qualities across the scale by focusing on the few exceptions. You’ll get:
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A clear breakdown of each interval across the scale
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Practice suggestions using adjacent strings
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A chart summarizing all outlier positions (in Roman numerals)
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A second chart for how to systematically practice every interval type across the neck
Diatonic 2nds (Stepwise Motion)
In C Major:
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C to D – major 2nd
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D to E – major 2nd
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E to F – minor 2nd
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F to G – major 2nd
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G to A – major 2nd
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A to B – major 2nd
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B to C – minor 2nd
In a major scale, most of the 2nds are major, with two exceptions: E–F and B–C, which are a half step apart.
Practice on Adjacent Strings:
Use string sets:
6–5, 5–4, 4–3, 3–2, 2–1
This helps you immediately see and hear the difference between a major 2nd (2-fret distance diagonally) and a minor 2nd (often same fret, one string up).
This layout is ideal for melodic shapes like:
C–D–C, D–E–D, C–D–C, B–C–B, C
By visualizing intervals across adjacent strings, you can easily repeat and ornament ideas.
Outliers:
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III, VII = minor 2nds
(All other scale degrees produce major 2nds)
As we move through each interval type (2nds, 3rds, etc.), you’ll notice that most intervals of a given type in the scale have the same quality—for instance, most diatonic 2nds in a major scale are major 2nds, but a couple are minor 2nds.
Rather than memorizing all seven intervallic relationships individually, it’s much easier to just remember:
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What the default quality is for each interval type (e.g., “most 2nds are major”)
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Which scale degrees deviate from that pattern
Those deviations are what we’ll call outliers.
So if the outliers for 2nds are minor, you can assume all the non-outliers are major. This is just a shortcut—a decluttering tool to reduce what you have to memorize while giving you the big picture.
Diatonic 3rds
In C Major:
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C to E – major 3rd
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D to F – minor 3rd
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E to G – minor 3rd
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F to A – major 3rd
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G to B – major 3rd
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A to C – minor 3rd
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B to D – minor 3rd
The 3rds alternate in quality: three of them are major, and the rest are minor.
Practice on Adjacent Strings:
Start on each string pair from 6–5 through 2–1. For example:
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C (8th fret 6th string) to E (7th fret 5th string) = major 3rd
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D to F = minor 3rd
Play them both ascending and descending to hear the unique character of each shape.
Outliers:
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I, IV, V = major 3rds
(All others are minor 3rds)
Diatonic 4ths
In C Major:
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C to F – perfect 4th
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D to G – perfect 4th
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E to A – perfect 4th
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F to B – augmented 4th
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G to C – perfect 4th
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A to D – perfect 4th
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B to E – perfect 4th
Most of the 4ths in a major scale are perfect, but the interval from F to B is the exception: it’s an augmented 4th (also known as a tritone).
Practice on Adjacent Strings:
Perfect 4ths are abundant in standard tuning—this interval is literally built into the guitar layout. However, F to B will look and sound different.
Try combining perfect 4ths with the tritone in a lick or comping pattern to contrast the stability of the 4th with the tension of the augmented 4th.
Outlier:
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IV = augmented 4th
(All others are perfect 4ths)
Diatonic 5ths
In C Major:
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C to G – perfect 5th
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D to A – perfect 5th
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E to B – perfect 5th
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F to C – perfect 5th
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G to D – perfect 5th
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A to E – perfect 5th
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B to F – diminished 5th
The only 5th that’s not perfect is B to F, which is a diminished 5th—the other half of the tritone.
Practice on Adjacent Strings:
Start with string sets 6–5 through 2–1, then try split string sets like 6–4 or 5–3 for wider spacing (see full routine below).
Outlier:
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VII = diminished 5th
(All others are perfect 5ths)
Diatonic 6ths
In C Major:
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C to A – major 6th
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D to B – major 6th
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E to C – minor 6th
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F to D – major 6th
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G to E – major 6th
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A to F – minor 6th
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B to G – minor 6th
This interval flips from major to minor three times.
Practice on Split String Sets:
These wider intervals benefit from spacing across strings like:
6–4, 5–3, 4–2, 3–1
Try practicing in a melodic way—6ths often appear in horn lines, ballads, and soul grooves.
Outliers:
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III, VI, VII = minor 6ths
(All others are major 6ths)
Diatonic 7ths
In C Major:
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C to B – major 7th
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D to C – minor 7th
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E to D – minor 7th
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F to E – major 7th
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G to F – minor 7th
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A to G – minor 7th
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B to A – minor 7th
Only two scale degrees produce major 7ths—the rest are minor.
Practice on Split String Sets:
These work beautifully over:
6–4, 5–3, 4–2, 3–1
You can also hear them as tension notes resolving upward.
Outliers:
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I, IV = major 7ths
(All others are minor 7ths)
Diatonic Octaves
Octaves are consistent across the scale. You’re simply playing the same pitch class one octave higher.
Practice on Adjacent Strings:
Octave shapes fall naturally across:
6–4, 5–3, 4–2, 3–1
Octaves are perfect intervals by default in diatonic major scales.
Diatonic Interval Outlier Summary
The table below shows which scale degrees are outliers for each interval type. The quality listed refers only to the outlier. All other degrees produce the opposite quality.
This is a shortcut to declutter your thinking and help you retain the big-picture structure of each interval type.
| Interval | Outlier(s) | Quality of Outlier(s) |
|---|---|---|
| 2nds | III, VII | Minor 2nds |
| 3rds | I, IV, V | Major 3rds |
| 4ths | IV | Augmented 4th |
| 5ths | VII | Diminished 5th |
| 6ths | III, VI, VII | Minor 6ths |
| 7ths | I, IV | Major 7ths |
| Octaves | — | All Perfect |
Interval Practice Routine: Adjacent and Split String Sets
To thoroughly internalize these intervals, follow this consistent guitar practice system:
| Interval Type | String Sets to Practice |
|---|---|
| 2nds | 6–5, 5–4, 4–3, 3–2, 2–1 |
| 3rds | 6–5, 5–4, 4–3, 3–2, 2–1 |
| 4ths | 6–5, 5–4, 4–3, 3–2, 2–1 |
| 5ths | 6–5, 5–4, 4–3, 3–2, 2–1 and 6–4, 5–3, 4–2, 3–1 |
| 6ths | 6–4, 5–3, 4–2, 3–1 |
| 7ths | 6–4, 5–3, 4–2, 3–1 |
| Octaves | 6–4, 5–3, 4–2, 3–1 |
Run each interval type on its recommended string sets, ascending and descending. You’ll develop melodic flexibility, ear training, and fretboard fluency—skills that translate directly to better improvising, composing, and musical intuition.
Interval Inversions: Your Shortcut to Total Mastery
So far we’ve mapped out every diatonic interval in the major scale and identified where the outliers live. That’s a lot of information. But here’s the good news:
You don’t have to memorize all 7 interval types independently.
Why? Because intervals have a special built-in relationship: they exist in inversion pairs. For every interval, there is another interval that completes the octave in reverse order, and the qualities flip.
The Rule of 9
Every interval and its inversion adds up to 9. For example:
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A major 2nd inverts to a minor 7th
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A minor 3rd inverts to a major 6th
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A perfect 4th inverts to a perfect 5th
This means that if you thoroughly understand the behavior of 3rds, 5ths, and 7ths, then you automatically know everything you need about:
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2nds (inverse of 7ths)
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4ths (inverse of 5ths)
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6ths (inverse of 3rds)
Interval Inversion Table
| Interval | Inverts To | Quality Flip |
|---|---|---|
| Minor 2nd | Major 7th | Minor ↔ Major |
| Major 2nd | Minor 7th | Major ↔ Minor |
| Minor 3rd | Major 6th | Minor ↔ Major |
| Major 3rd | Minor 6th | Major ↔ Minor |
| Perfect 4th | Perfect 5th | Perfect ↔ Perfect |
| Augmented 4th | Diminished 5th | Aug ↔ Dim |
| Diminished 5th | Augmented 4th | Dim ↔ Aug |
| Perfect 5th | Perfect 4th | Perfect ↔ Perfect |
| Minor 6th | Major 3rd | Minor ↔ Major |
| Major 6th | Minor 3rd | Major ↔ Minor |
| Minor 7th | Major 2nd | Minor ↔ Major |
| Major 7th | Minor 2nd | Major ↔ Minor |
Just add the numbers:
2 + 7 = 9
3 + 6 = 9
4 + 5 = 9
Etc.
Now, instead of learning all seven interval types independently, you only need to memorize the 3 core ones: 3rds, 5ths, and 7ths—and their inverted partners fall right into place.
The Harmonic Backbone: Diatonic Chord Qualities
Let’s look at the harmonized major scale using Roman numerals and chord symbols. This is the system you already know—and it contains all the interval information you need.
Diatonic 7th Chords in a Major Key:
| Roman Numeral | Chord Quality |
|---|---|
| I | Maj7 |
| II | min7 |
| III | min7 |
| IV | Maj7 |
| V | 7 (dominant) |
| VI | min7 |
| VII | min7♭5 |
From this, you automatically know:
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Which scale degrees have major or minor 3rds (based on chord quality)
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Which have perfect, diminished, or augmented 5ths
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Which have major or minor 7ths
So for example:
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The I chord (Maj7) includes a major 3rd, perfect 5th, and major 7th
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The II chord (min7) includes a minor 3rd, perfect 5th, and minor 7th
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The VII chord (min7♭5) includes a minor 3rd, diminished 5th, and minor 7th
From this framework, you can deduce all interval qualities by looking at what role a note plays in the chord structure.
Example: 4ths in the Key of A
Let’s say you want to practice 4ths in the key of A major. Instead of memorizing each interval directly, you can think in reverse by relating them to 5ths—which are easier to track through chord function.
Here’s the A major scale:
A – B – C♯ – D – E – F♯ – G♯
Now look at this example:
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A to D is a perfect 4th.
But what if you think of it as a 5th below the IV chord (Dmaj7)?
Then it’s the interval from the 5th (A) to the root (D).
Same sound—different perspective. -
B to E is a perfect 4th, and that’s the 5th on the V chord (E7) in reverse.
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G♯ to C♯ is a perfect 4th—and that’s the diminished 5th on the VII chord (G♯min7♭5).
By thinking in inversion pairs, you reduce memory load and reinforce your harmonic understanding. You’re not just memorizing shapes—you’re hearing chord function, interval color, and melody all working together.
Final Takeaway: Boil It Down
If you thoroughly understand how the 3rds, 5ths, and 7ths behave in a major key—via the harmonized scale—you’ve already got everything you need. Just apply these two tools:
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Memorize Outliers
Use the outlier chart to quickly see where things deviate in the diatonic structure. -
Use Inversions
Think of 2nds as inverted 7ths, 4ths as inverted 5ths, and 6ths as inverted 3rds.
This approach lets you focus on the core structures—and trust the rest to fall into place.
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