Tutorial · 3 of 5 · Theory
Major and minor harmonic field
The harmonic field is the set of chords that "live" in a key. Knowing those chords is the quickest shortcut to composing, improvising and figuring out songs by ear.
Where chords come from
Take a scale, for example C major: C, D, E, F, G, A, B. On top of each note, stack two more notes from the same scale, skipping one each time. On C you get C, E and G, which is the C major chord. On D you get D, F and A, which is D minor. Doing this with all seven notes gives you seven chords. That set is the harmonic field of C major, also called the diatonic chords of the key.
Major harmonic field
In any major key, the sequence of chord types is always the same: major, minor, minor, major, major, minor, diminished. Roman numerals show the degree of each chord; upper case for major chords, lower case for minor ones.
| Degree | I | ii | iii | IV | V | vi | vii° |
|---|---|---|---|---|---|---|---|
| Triads in C | C | Dm | Em | F | G | Am | B° |
| Seventh chords in C | Cmaj7 | Dm7 | Em7 | Fmaj7 | G7 | Am7 | Bm7(♭5) |
| Triads in G | G | Am | Bm | C | D | Em | F♯° |
Notice that G major follows exactly the same pattern, just starting on another note. That's why, once you memorize the pattern, you know the harmonic field of all 12 major keys.
The three functions
The chords in the field don't all play the same role. Harmony works like a story of rest, departure and tension:
- Tonic (I, vi, iii): a feeling of home, of rest. In C: C, Am and Em.
- Subdominant (IV, ii): departure, the music leaves home. In C: F and Dm.
- Dominant (V, vii°): tension that wants to return to the tonic. In C: G and B°. G7, with the seventh, makes that tension even stronger.
Most popular songs alternate between these three functions. When you hear G7 going to C, your ear feels the arrival home.
Minor harmonic field
The A natural minor scale (A, B, C, D, E, F, G) uses the same notes as C major. That's why A minor is the relative key of C major: the two share the same chords, only which one is home changes.
| Degree | i | ii° | III | iv | v | VI | VII |
|---|---|---|---|---|---|---|---|
| Natural minor in A | Am | B° | C | Dm | Em | F | G |
| With harmonic minor | Am | B° | C+ | Dm | E7 | F | G♯° |
In natural minor, the fifth degree is minor (Em) and the pull back to Am is weak. That's why it's very common to raise G to G sharp, which forms the harmonic minor scale. With that, the fifth degree becomes E or E7, a real dominant. In practice, songs in a minor key mix both versions freely.
How to use this day to day
- To compose: pick a key and stay inside the field. Any sequence of those seven chords sounds coherent.
- To figure out songs: find the first chord (usually the I or the i). The next ones are almost always in the field of that key.
- To transpose: think in degrees instead of names. I–IV–V in C is C–F–G; in D, it's D–G–A.