Diatonic Chords, Explained

Lisa Witt  /  Guides / Jul 6

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What are diatonic chords? They sound fancy, don’t they? Well, not exactly! In a nutshell…

Diatonic chords are chords built on the notes of a particular scale.

The concept behind this is actually quite simple once you understand a few basic things about music theory. This article will explain in detail what diatonic chords are, how they work, and why they’re an important concept for all piano players.

Table of Contents:

  1. Scales (A Review)
  2. How to Build Diatonic Chords in C Major
  3. How to Build Diatonic Chords in Other Keys
  4. The Number System
  5. How to Use Diatonic Chords

If you like watching more than reading, check out the video above. If you want a deeper dive into theory, keep reading!

1. Scales (A Review)

To understand diatonic chords, we first have to understand scales. Scales are a sequence of notes organized by pitch. Often, a formula or set of rules determine how the notes are ordered.

The most common types of scales include:

Each of these types of scales has its own unique formula.

The Major Scale Formula

For the purposes of this lesson, we’ll focus on the major scale.

You can build a major scale starting on any note, whether black or white key, on the piano using the same formula:


The “W” stands for “whole step” and the “H” stands for “half step.” A half step is the distance between two keys that are immediately next to each other. A whole step is made up of two half steps.

Keyboard diagram with half steps and whole steps highlighted and labelled. Example: E and F is half step, C to D is whole step.

So, taking this formula, we’ll start on C, move up a whole step to D, move up another whole step to E, and so on.

Using this formula, these are the notes to the C Major scale:

Keyboard diagram of the C major scale with note names and scale degree numbers labelled. CDEFGAB is 1234567. Distance between each key is labelled as whole step (W) or half step (H).

In other words, all the white keys. We can also assign a number to each note. C is the first note of the C Major scale, D is the second note, and so on. You might hear these numbers being referred to as degrees of the scale.

If you want to get really fancy, music theory experts have special names for each degree of the scale:

1 – Tonic
2 – Supertonic
3 – Mediant
4 – Subdominant

5 – Dominant
6 – Submediant
7 – Leading Tone

Don’t worry too much about these terms for now. You may, however, run into them at some point — like when learning dominant 7th chords.

2. How to Build Diatonic Chords

Building diatonic triads is a simple matter of stacking triads (three-note chords) on top of each degree of the scale:

C major diatonic triads in the treble clef on the musical staff.

You can easily find all these chords on your piano by playing the triad claw-shape on every note of the C Major scale. Like this:

And here are the notes written out:

Degree of Scale (C Major)Diatonic Triad
1 – C (tonic)C-E-G
2 – D (supertonic)D-F-A
3 – E (mediant)E-G-B
4 – F (subdominant)F-A-C
5 – G (dominant)G-B-D
6 – A (submediant)A-C-E
7 – B (leading)B-D-F

Try this yourself: play the C Major scale, then play the claw-shaped triad on top of every note. You’ll notice that some chords sound “happy” and some chords sound “sad.” This is because some diatonic chords are major chords and others are minor chords.

Interestingly, in all major scales, certain diatonic chords will always be major or minor. There’s a way to visualize this, which we’ll cover shortly in the number system section.

But first, let’s quickly run over how to build triads on a scale with more sharps and flats. Like D Major.

But first, let’s quickly run over how to build triads on a scale with more sharps and flats. Like D Major.

🤿🎹 DIVE DEEPER: Did you know you can build any major or minor triad using the same formula? Learn how to build major and minor triads in this lesson.

🔥🎹 HOT TIP! New to chords? Check out our free Chording 101 guide and learn how chords are the backbone to virtually all piano music.

3. How to Build Diatonic Chords in Other Keys

Building diatonic chords in other keys is the same process as building them in C Major: go through each degree of the scale and play the triad claw shape on top.

The only difference is, you need to watch out for what notes to sharp or flat.

So, if you’re working with D Major, which has two sharps (F# and C#), each time you run into F or C, sharp them.

Degree of Scale (D Major)Diatonic Triad
1 – D (tonic)D-F#-A
2 – E (supertonic)E-G-B
3 – F# (mediant)F#-A-C#
4 – G (subdominant)G-B-D
5 – A (dominant)A-C#-E
6 – B (submediant)B-D-F#
7 – C# (leading)C#-E-G

4. The Number System

The number system allows you to quickly visualize whether a diatonic chord is major, minor, or something else. Here’s how we represent the diatonic chords of the major scale using Roman numerals:

I – ii – iii – IV – V – vi – viio

Each Roman numeral corresponds to a scale degree. The chords written in uppercase letters are major, and the chords written in lowercase letters are minor. Chords I, IV, and V are always major chords, and chords ii, iii, vi, and viio are always minor chords. This is true in all major keys.

❗💡 BONUS: What’s that circle symbol? The “o” in chord vii means it is a diminished chord. A diminished triad is a stack of minor thirds. This is in contrast to a minor triad, which contains a major third stacked on top of a minor third.

Why use the numbering system?

The numbering system may make music look more like math than art, but trust us, there’s a reason we use it!

Numbers allow musicians to seamlessly transpose a song from one key to another. Imagine this chord progression:

C – G – Am – F

This is a common progression in C major, but how do you play this in, say, G major?

Well, if we visualize each chord as a diatonic chord built on a scale degree…

I – V – vi – IV

…we can substitute G major chords based on these numbers!

G – D – Em – C

G is the I chord of G Major. D is the V chord of G Major, and so on.

5. How to Use Diatonic Chords

So…what’s the point to all this theory?! Good question!

Diatonic chords help you answer this age old question:

What chords sound good with this song?!

If you know all the diatonic chords of a key, you’ll know what chords will sound good in that key! This opens up many possibilities for chording, songwriting, and improvising.

Knowing these chords will also give you a head start in figuring out the chords of a song. Say you’re trying to figure out the chords to a song in D Major by ear. By writing or playing out all the diatonic chords in D Major, you can narrow down which chords will show up in your song.

Next Steps

We’ve demonstrated how to find diatonic chords in C Major and D Major. Now it’s your turn! See if you can find the diatonic chords in these keys: G Major, F Major, and B Flat Major. Then, find a song you’d like to play in one of these keys, and see if you can figure out the chords by ear!

Charmaine Li is a Vancouver writer who has played piano for over 20 years. She holds an Associate diploma (ARCT) from the Royal Conservatory of Music and loves writing about the ways in which music—and music learning—affects the human experience. Charmaine manages The Note.

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