Start from seven actual notes
To find the diatonic chords of C major, write C, D, E, F, G, A, B. Choose a starting note and take every other scale note until you have three. Starting on C gives C, E, G. Starting on D gives D, F, A. Continue around the same collection.
The scale supplies the notes; interval distances supply each chord’s quality. You are not adding the same major-chord shape above every degree. That would introduce notes outside the collection.
Read the resulting qualities
C–E–G is major because its third is four semitones above C. D–F–A is minor because F is three semitones above D. B–D–F has both a minor third and a diminished fifth, making it diminished.
The complete pattern in a major key is major, minor, minor, major, major, minor, diminished. Roman numerals express the degrees and qualities together.
| Degree | Chord | Notes |
|---|---|---|
| I | C | C · E · G |
| ii | Dm | D · F · A |
| iii | Em | E · G · B |
| IV | F | F · A · C |
| V | G | G · B · D |
| vi | Am | A · C · E |
| vii° | Bdim | B · D · F |
Transfer the method to D major
D major contains D, E, F-sharp, G, A, B, C-sharp. Stacking the same degrees now gives D, Em, F-sharp minor, G, A, Bm and C-sharp diminished. The chord names change but the quality pattern stays the same.
Check the ii chord: E, G, B contains no F-sharp or C-sharp, even though the key signature has both. A chord uses selected notes from the key; it need not include every accidental in the signature. Conversely, the V chord A–C-sharp–E must retain C-sharp.
Continue the stack once more
Adding another scale third to each triad gives a seventh chord. In C major the results are Cmaj7, Dm7, Em7, Fmaj7, G7, Am7 and Bm7-flat-5. Notice that the sevenths are not all the same quality.
For example, C to B is a major seventh, while D to C is a minor seventh. The vii chord adds A to B–D–F, producing a half-diminished seventh. Keep its minor seventh distinct from the diminished seventh of a fully diminished chord.
Name the minor collection before stacking
A natural minor yields E minor on its fifth degree because it contains G natural. A harmonic minor contains G-sharp and therefore yields E major on that degree. Neither table should be labeled merely “all minor-key chords” without saying which collection was used.
Real minor harmony often uses more than one form. The tool lets you inspect a chosen collection, while a musical analysis still needs the surrounding phrase and its actual notes.
The result is a collection of available diatonic chords, not a ranking of which chord must come next. For example, Am belongs to C major and can also serve as a tonic in A minor. Hearing or seeing Am once does not settle the key. Check the complete phrase, the emphasized tonic and any altered notes before turning a table lookup into an analysis.
Build a small progression you can verify
Arrange C–F–G–C, keeping the same duration for each chord. Then transpose the exercise to D–G–A–D. Read the notes in each result and check the shared I–IV–V–I degree pattern.
- Write the scale before looking at the chord table.
- Stack degrees 1, 3 and 5 from each starting point.
- Classify the third and fifth rather than guessing from a symbol.
- Add a seventh and check its distance from the root.
Sources and methods
Put it into practice.
Explore these notes and relationships in the interactive tools.