How Scales Are Born From Chords (1 Chord, 2 Chords, 3 Chords)
A triad is an unfinished scale: it gives you three of a scale's seven notes, so one chord leaves four notes open to choice, two chords narrow the options, and three chords usually decide the scale.
Key points
- A triad gives three of a scale's seven notes, so four notes are left to your choice.
- One chord such as D major fits D major, mixolydian, lydian and harmonic major, and it is also the V of G harmonic and melodic minor.
- Two chords narrow the options. D major with G major gives D major, D mixolydian or G harmonic major.
- Three chords such as D, G and B minor decide the scale, and the same trio can belong to two keys with different functions.
- Practise by holding a chord in the left hand and running every scale that fits in the right hand.
Most students learn scales through tone–tone–semitone formulas or through modes. In this lesson Jason Zac of Nathaniel School of Music builds scales a different way: from chords. It suits pianists who read chord charts, improvise or compose, and who want to know which scales fit over a given chord.
The core idea: a chord is an unfinished scale
A triad gives you three notes, and a scale needs seven. That leaves four notes for you to choose. The more chords you combine, the fewer notes are left open, until the scale is decided. This is how chord charts work: you read the chords and interpret the scale. You are not locked to the key signature. The chord, a pair of chords (a cadence) or a group of three can point to major one day, harmonic major the next and mixolydian after that.
Step 1: Gather chords around one anchor note
Pick a single note. The lesson uses D. Then list every major and minor triad that contains it:
- D major: D F# A
- D minor: D F A
- G major: G B D
- G minor: G Bb D
- Bb major: Bb D F
- B minor: B D F#
This group is the chord tree of D, and every example below comes from it.
Step 2: One chord leaves four notes open
Take D major on its own. Scales with D as the tonic include D major, D mixolydian, D lydian and D harmonic major. The chord also works in scales where D is not the tonic. It is the dominant (V) of G harmonic minor and G melodic minor.
G minor works the same way. You can treat it as a tonic, or as the subdominant (iv) of a scale such as D phrygian (D Eb F G A Bb C). Bb major on its own opens up Bb major, Bb harmonic major, Bb mixolydian and Bb lydian.
Step 3: Two chords narrow it down
Combine two chords from the tree and only one or two notes stay open.
- D major + G major gives D, F#, A, G and B. If D is the tonic, you can play D major or D mixolydian. If you make G the tonic, with D as its dominant, the pair also fits G harmonic major (G A B C D Eb F#).
- D major + G minor leads to the less common colours. Hear it as D7 resolving to G minor and you get G harmonic minor or G melodic minor. With D as the tonic, it fits D harmonic major (D E F# G A Bb C#).
- D major + Bb major puts F# and F side by side. That points to an unusual scale, and it is worth exploring by ear.
- D major + B minor share two notes, so they behave very simply.
Avoid pairing namesake chords such as D major with D minor, because the result sounds odd.
Step 4: Three chords decide the scale
With three chords the gaps close. D major, G major and B minor belong to both D major and G major, and only their functions change.
- In D major: D is the tonic (I), G the subdominant (IV) and B minor the submediant (vi).
- In G major: G is the tonic (I), B minor the mediant (iii) and D the dominant (V).
The same trio can also work with G harmonic major.
D minor, G minor and Bb major belong to several scales:
- In Bb major: iii, vi and I.
- In F major: vi, ii and IV.
- In D natural or harmonic minor: i, iv and VI.
How to practise
- Hold a chord in the left hand, or just play its root.
- With the right hand, run each scale that could fit over it, and listen to the colour each one gives.
- Repeat with pairs of chords, then with trios, and notice how the choices shrink.
- Once D feels comfortable, choose another anchor note and build its chord tree. There are 12 to explore.
Questions about this lesson
How can a chord tell me which scale to play?
A triad already supplies three of the seven notes of a scale. The scales that fit are the ones containing those three notes, and the remaining four notes are your choice.
What scales work over a D major chord?
With D as the tonic, D major, D mixolydian, D lydian and D harmonic major all work. D major is also the dominant chord of G harmonic minor and G melodic minor, so those scales fit too.
Which scales fit D major and G major together?
If D is the tonic, you can use D major or D mixolydian. If G is the tonic, with D as its dominant, G harmonic major also fits.
Why do D, G and B minor fit two different keys?
All three chords belong to both D major and G major. In D major they are I, IV and vi, and in G major they are V, I and iii.
Practise it
- Chord TreesStart from a note and explore related chords, inversions and voicings.
- CantusChoose a root and scale, hear piano voicings, and move the same shape through different intervals.
- Piano classes at Nathaniel School of MusicLive online or in Bangalore, with a teacher.
- All free music apps40 practice tools for harmony, rhythm, ear training and more.
Related lessons
- How to Transpose to Any Key, Scale, Mode and Chord Progression on PianoTo transpose a melody on piano, first choose its tonic and scale, write each note as a scale-degree number (or swara), then rebuild those numbers in a new key, a new scale, a new mode or over a new chord, singing it before you play it.
- How to Creatively Practise Thirds Over Piano ScalesTo practise thirds over a piano scale, write the scale in a circle, pair each note with the scale note two steps above it (E with G#, F# with A, and so on in E major), then play those pairs up, down, or in mixed directions to build both technique and melody.
- Explore the Y-Axis of Music With All Intervals and Scales Using a Simple Chord ProgressionThe pendulum scale drill trains you to move both above and below the root (one, two, three and four steps each way from F), then harmonise the right-hand pattern with a left-hand tonic, predominant and dominant chord in major, minor and modal scales.
- How to Creatively Practise Finger Crossovers for Piano Scales (The Pendulum)The Pendulum is a piano exercise where your thumb anchors on the root of a scale and your fingers swing one, two, three, then four notes above and below it, training thumb-under and finger-over crossovers while teaching you to hear the scale on both sides of the root.