What Is Diatonic?
The chord "team" that makes your songs feel like they belong to one key
1) Why knowing diatonic chords changes everything
Maybe you've done this:
You know a handful of chords —
C, G, F, Am, Dm, Em, E, A, B7…
So you just string them together and see what happens.
- Each chord sounds okay on its own, but
- The progression doesn't really feel like one coherent song
- And when you hit something nice, it's hard to recreate it later
One big reason is:
> You're mixing chords that belong to the key > with chords that are outside the key.🎯 Even if you play "by ear," diatonic makes it repeatable
If your ears are good, you may stumble into great progressions just by feel.
But:
- Why did that one sound good?
- How do you get a similar mood in a different key, on another day?
Without a framework, you're relying on luck each time.
> When you know diatonic chords, you can say: > "Oh, that nice progression was actually I → V → vi → IV," > and you can rebuild it on purpose, in any key.2) From scale to chord "team"
From "What Is a Scale?", recall the C major scale:
- Scale: C D E F G A B
- Degrees: 1 2 3 4 5 6 7
Using only these notes, stack 3rds and build triads. You get seven chords –
the C major diatonic team:
- From C: C–E–G → C (major)
- From D: D–F–A → Dm (minor)
- From E: E–G–B → Em (minor)
- From F: F–A–C → F (major)
- From G: G–B–D → G (major)
- From A: A–C–E → Am (minor)
- From B: B–D–F → Bdim (diminished)
| Degree | Chord | Type | Rough feeling |
|---|---|---|---|
| 1st | C | Major | Strongest sense of "home" |
| 2nd | Dm | Minor | Getting ready to move |
| 3rd | Em | Minor | Light, floating upward |
| 4th | F | Major | Forward, open motion |
| 5th | G | Major | Wants to go somewhere |
| 6th | Am | Minor | Melancholic "alternate home" |
| 7th | Bdim | Diminished | Unstable, needs to resolve |
3) Roman numerals: one formation for every major key
Rewrite the C major team using Roman numerals:
- I … C
- ii … Dm
- iii … Em
- IV … F
- V … G
- vi … Am
- vii° … Bdim
| Symbol | Meaning | Type |
|---|---|---|
| I | 1st-degree chord | Major |
| ii | 2nd-degree chord | Minor |
| iii | 3rd-degree chord | Minor |
| IV | 4th-degree chord | Major |
| V | 5th-degree chord | Major |
| vi | 6th-degree chord | Minor |
| vii° | 7th-degree chord | Diminished |
Key observations:
- This pattern I–ii–iii–IV–V–vi–vii° is the same in every major key.
- Only the note names change.
Example: in G major,
- Scale: G A B C D E F#
- Diatonic chords: G, Am, Bm, C, D, Em, F#dim
- Roman numerals: still I, ii, iii, IV, V, vi, vii°
That's diatonic thinking:
learn one formation, reuse it everywhere.
4) Positions in the team: Tonic / Subdominant / Dominant
Inside the team, chords have functional roles:
- Tonic (T) – home, rest, resolution
- Subdominant (S) – movement away from home
- Dominant (D) – strong pull back toward home
In C major:
- Tonic group: C (I), Am (vi)
- Subdominant group: Dm (ii), F (IV)
- Dominant group: G (V), Bdim (vii°)
Typical patterns
- T → S → D → T
- e.g. C → F → G → C
- T → D → T
- e.g. C → G → C (simple but powerful)
- Start from vi for a bittersweet feel
- e.g. Am → F → G → C (vi → IV → V → I)
A huge number of rock and pop songs are built from
these team positions: T, S, D – just in different orders.
5) Diatonic × Ear training × Improvisation
🦻 Ear training: practical picture
1. Listen and guess the key: maybe C? maybe G?
2. If you think it's C major, test chords from the C major team:
C, Dm, Em, F, G, Am, Bdim.
3. If the last chord of the chorus is G → C and it feels very final,
you can guess that's V → I.
So diatonic chords become:
> Not "all possible chords," but > a focused set of likely answers.🎸 Improvisation: what to play over the team
Once you know the diatonic team:
- A progression like C → Am → F → G
reads as I → vi → IV → V.
- You can choose scales logically:
C major scale, A minor pentatonic, etc.
Then you can refine:
- Over T, land on 1 or 3 for stability
- Over D, use 7 or tensions for extra pull before going back to T
6) Visualizing the diatonic team in OtoTheory's "Find Chords"
In OtoTheory, you don't have to calculate diatonic chords by hand.
You can see and hear the whole team in one place.
- Open the "Find Chords" screen.
- Choose a key and a scale.
- The app shows you the diatonic chord team for that key as a list of cards.
- Tap any card to hear the chord right away.
On the fretboard below:
- All scale tones for the selected scale are shown, and
- When you tap a diatonic chord, its chord tones are highlighted on top of that scale.
So you can literally see:
> "While this chord is playing, > which notes on the fretboard will match easily with it?"This is useful not only for:
- Learning how diatonic chords work visually and by ear, but also for
- Writing chord progressions when composing, and
- Building guitar solo ideas when you practice improvisation.
7) Summary & a small next step
- Diatonic = the chord team built only from a key's scale.
- Progressions that stay mostly inside this team
naturally feel like they belong to one key.
- Roman numerals give a key-independent formation:
I–ii–iii–IV–V–vi–vii°.
- Inside the team, Tonic/Subdominant/Dominant describe
how each chord moves the story.
- For ear training, improvisation, and songwriting,
diatonic chords act as smart first guesses, not random stabs in the dark.
🎒 A tiny assignment
- Pick one song you like.
- Try to guess its key (C? G? D?) by ear.
- In OtoTheory, load the diatonic team for that key.
- See how many chords in the song come from that team.
Next Steps
- Review the basics of scales → "What Are Scales?"
- Understand the relationship between keys and scales → "What Is a Key?"
- Learn the basics of chords → "What Are Chords?"
- Understand intervals → "What Are Intervals?"
- Get an overview of music theory → "What Is Music Theory?"