Triad Basics

A triad is a three-note chord built by stacking two thirds.

A major 3ʳᵈ = 4 half-steps (E–G♯)
A minor 3ʳᵈ = 3 half-steps (E–G)

Four combinations of stacked thirds produce the four basic triads:

• Major: 1–3–5 = Major 3ʳᵈ + Minor 3ʳᵈ (C–E–G)
• Minor: 1–♭3–5 = Minor 3ʳᵈ + Major 3ʳᵈ (C–E♭–G)
• Diminished: 1–♭3–♭5 = Minor 3ʳᵈ + Minor 3ʳᵈ (C–E♭–G♭)
• Augmented: 1–3–♯5 = Major 3ʳᵈ + Major 3ʳᵈ (C–E–G♯)

Major and minor triads contain one major and one minor 3ʳᵈ, only the order changes. Diminished and augmented triads contain two identical thirds. Major and minor triads are also the only triads that contain a perfect 5ᵗʰ.

Triads in the Major Scale

Harmonizing a major scale produces the following triads:

I–ii–iii–IV–V–vi–vii°
Major–Minor–Minor–Major–Major–Minor–Diminished

Capital Roman numerals represent major triads, lowercase represent minor, and ° represents diminished.

First Third

Let’s first locate the interval between the root and the 3ʳᵈ.

(Insert Major Scale First-Third Diagram)

A clear pattern appears.

Major 3ʳᵈs: built on 1, 4, 5

Minor 3ʳᵈs: built on 2, 3, 6, 7

The same relationship appears in C minor.

Here’s a look at the portion of the fretboard but in C minor:

In a minor key, the major triads occur on:

♭3, ♭6, ♭7

The remaining triads begin with minor 3ʳᵈs.

Harmonizing a Major Scale

Each triad is completed by stacking another 3ʳᵈ above the first.

Triads in the Major Scale

I (Major): 1–3–5
ii (Minor): 2–4–6
iii (Minor): 3–5–7
IV (Major): 4–6–1
V (Major): 5–7–2
vi (Minor): 6–1–3
vii° (Diminished): 7–2–4

The pattern now becomes clear.

Major triads (I, IV, V):
Major 3ʳᵈ + Minor 3ʳᵈ

Minor triads (ii, iii, vi):
Minor 3ʳᵈ + Major 3ʳᵈ

Diminished triad (vii°):
Minor 3ʳᵈ + Minor 3ʳᵈ

The NANDI Method

Using the fourth pattern, thirds become simple movements across the fretboard.

Major 3ʳᵈ
One fourth higher, one half-step lower

Minor 3ʳᵈ
One fourth higher, two half-steps lower

Moving in the opposite direction simply inverts the relationship.

Major 3ʳᵈ
One fifth lower, one half-step higher

Minor 3ʳᵈ
One fifth lower, two half-steps higher

Once these two interval movements are understood, every major, minor, diminished, and augmented triad can be derived without memorizing chord shapes.

Crossing the B String

The same principles apply across the G–B–E strings.

(Insert B-String Diagram)

Because the B string is tuned one half-step lower than the other string pairs, every familiar pattern shifts by one fret when crossing the B string.

The completed triads appear below.

Understanding this one adjustment allows the same NANDI interval logic to be applied anywhere on the fretboard.