Chord Fundamentals

In the last lesson — How Major Scales Work — you built the C major scale from a single formula. A scale gives you melody — one note after another. Now stack some of those notes on top of each other instead of playing them in a line, and you get harmony: a chord. Chords are what give music its mood, its colour, and its sense of arriving "home".

There are two ways to see how a chord is built. The first is quick and grows straight out of the scale you just learned — we’ll start there and have a chord under your fingers in seconds. The second is a little deeper: it works in any key at all and explains why the chords sound the way they do. You need no note-reading and no MIDI keyboard for either; a mouse or touchscreen is enough.

The major chord — straight from the scale

Write out the C major scale and number the notes 1 to 7 — the scale degrees you met last time: C(1) D(2) E(3) F(4) G(5) A(6) B(7). Now play just the 1st, 3rd and 5th notes together — C, E and G. Skip a note, skip a note. That is C major, the most important chord in music, written simply C.

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Because it is built from the 1st, 3rd and 5th degrees of the scale — 1, 3, 5 — this chord sits perfectly at home in the key of C.

To play it, your right hand falls naturally into place: thumb (1) on the root C, middle finger (3) on E, little finger (5) on G. There is a neat coincidence worth remembering — the fingers you use, 1, 3 and 5, are the very same numbers as the scale degrees. Your left hand simply mirrors it: little finger (5) on C, middle finger (3) on E, thumb (1) on G. And here is the time-saver: this same 1–3–5 shape plays every root-position triad — major, minor, augmented or diminished — only the keys underneath it change.

Press play to hear the three notes climb, then ring out together:

Minor — lower the third

Here is the surprise: to turn C major into C minor you change just one note. Take the middle note — the 3rd — down a single half step, from E to E♭. The root (C) and the 5th (G) do not move at all.

The 3rd is the note that decides a chord’s mood. Leave it high and the chord is bright and happy; lower it and the chord turns dark and wistful. That one half step is the whole difference between triumphant and tender. Below, the root and fifth keep the first colour and the lowered 3rd is picked out in the second:

Hear how much darker the same shape sounds with that single note lowered:

The deeper way — a third is an interval

So far we have leaned on the scale: "take the 1st, 3rd and 5th, then lower the 3rd for minor." That is quick — but it only works once you already know the scale. There is a second, more powerful way to see the very same chords, one that works from any note, even one whose scale you have never played.

The gap between the root and that middle note has a name: a third. A third simply means skip one letter — C up to E steps over D. And a third comes in two sizes:

• A major third — written M3, a capital M for major — spans four half steps. C up to E is a major third: count the keys you pass, C♯, D, D♯, then E.

• A minor third — written m3, a small m for minor — spans three half steps, one fewer. C up to E♭ is a minor third: only C♯ and D sit between them.

Here is the major third — C to E, four half steps apart (the keys in between shown in the second colour):

And the minor third — C to E♭, one key smaller:

Now the magic behind minor makes sense: lowering the 3rd from E to E♭ shrank the lower third from a major third into a minor third. It is still a third — still an interval of a third — but a half step narrower: three half steps now instead of four. That narrower size is the darker mood.

Two stacked thirds — and the last two chords

Look at C major again as intervals. From C to E is a major third; from E up to G is a minor third. A triad is simply two thirds stacked on top of each other — root, a third, then another third — piled up like a little snowman. And because each of the two thirds can be major or minor, there are exactly four ways to stack them:

• Major = M3 + m3 — a major third, then a minor third on top

• Minor = m3 + M3 — the same two thirds, swapped over

• Augmented = M3 + M3 — two major thirds

• Diminished = m3 + m3 — two minor thirds

Notice the symmetry: major and minor each use one third of each size — they simply swap the order — while augmented and diminished each use two of the same. You have already built the first two; the other two — the chords this interval view explains best — are next.

Augmented stacks two major thirds. Take C major and raise the top note, G up to G♯. Both thirds are now major, the chord loses its resting point, and it sounds suspended, floating, unfinished:

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Diminished stacks two minor thirds. Take C minor and lower the top note too, G down to G♭. Both thirds are now minor, and the chord turns tight and tense — the sound of suspense in film music:

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A quick way to remember the rare two: augmented is "stretched" — its outer notes are wider apart than a normal fifth — while diminished is "squeezed", narrower. Stretched sounds floaty, squeezed sounds tense.

So here are the same four chords, seen both ways at once:

• Major — degrees 1 · 3 · 5, or M3 + m3 (C E G)

• Minor — 1 · ♭3 · 5, or m3 + M3 (C E♭ G)

• Augmented — 1 · 3 · ♯5, or M3 + M3 (C E G♯)

• Diminished — 1 · ♭3 · ♭5, or m3 + m3 (C E♭ G♭)

See them side by side

Here are all four chords on C, written on the staff. Notice how alike they look — three notes stacked like a snowman — and that only the middle and top notes shift up or down. From left to right: C major, C minor, C augmented, C diminished.

Explore any chord live

Want to poke at a chord yourself? Open one in The Ultimate Piano’s Theory Bar, then change the root or the type and watch the notes light up on the keyboard — for all twelve keys:

The same law in every key

This is where the interval view really pays off. The recipes never change — only the starting note does — and you do not need to know every scale to use them. Stack a major third then a minor third on G and you get G major (G–B–D). Do the same from F, minor third first, and you get F minor (F–A♭–C).

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Same shape, same bright sound — just moved to a new home. With the two thirds in your fingers you can build any of the 48 basic triads (twelve roots × four types) without memorising a single one.

Practise it

Take it one hand at a time. Start with just your right hand and the 1–3–5 shape: press C, E and G down together, lift, and play it again until the shape feels natural. Then try C minor — same fingers, just slide the middle finger down to E♭ — and switch back and forth, listening for the 3rd flipping between bright and dark. Once that feels easy, add the augmented and diminished shapes. Only the notes move; your hand keeps the same 1–3–5 shape.

When the shapes come without thinking, bring in the metronome to work on timing — still just one hand. Set a slow, steady pulse and change chord cleanly on each click; accuracy first, speed later. Start around 70 BPM:

Later, once one hand feels comfortable, add the left hand — it plays the same chord lower down, fingered 5–3–1. Playing the chord in both hands together is a great next step, but there is no rush at all: a clean, confident one-hand chord comes first.

If you have a MIDI keyboard connected, the chord trainer names a chord and checks the notes you play. (No MIDI keyboard? Skip this one and simply build the chords by hand, naming the root, third and fifth out loud as you stack them.)

What you’ve learned — and what’s next

• Straight from the scale: degrees 1 · 3 · 5 give a major chord, and lowering the 3rd makes it minor.

• The deeper way: a chord is two thirds stacked, and the two sizes of third (major = four half steps, minor = three) combine four ways — major, minor, augmented and diminished.

• The 3rd decides the mood — a single half step turns major into minor.

• One hand shape: a root-position triad is played 1–3–5 in the right hand (5–3–1 in the left) — the same fingering for all four qualities.

• Both views agree, and the interval one travels to all twelve keys unchanged, just like the major-scale formula did.

Next, we’ll return to the C major scale and build a chord on every one of its notes. The result is a ready-made family of chords that all belong together — the foundation of almost every song you know. After that, you’ll learn to reshape these chords with inversions so they flow smoothly from one to the next. That’s the next two lessons: One Scale, Seven Chords and Chord Inversions.