CHORD FUNCTION & DEGREES

Why Chords Move the Way They Do

Chord Function & Degrees

In the previous lesson, you discovered that harmonizing the major scale always produces the same sequence of chord families: Maj7 — Min7 — Min7 — Maj7 — Dom7 — Min7 — m7b5. But knowing what chords exist in a key is only half the story. The other half is understanding why they behave so differently from each other.

The answer lies in chord function — the role each chord plays within the key. In jazz harmony, every chord belongs to one of three functional groups: Tonic, Subdominant, or Dominant. These three functions are the engine behind virtually every chord progression you'll ever play.

💡 This lesson builds directly on Harmonizing the Major Scale in 7th Chords. Make sure you're comfortable with the 7 diatonic chords before continuing.

The Three Functions

Tonic

Home. Stability. Rest. The chord the music wants to return to. It creates no tension — it resolves it.

Subdominant

Movement. Departure. The chord that steps away from home — gentle enough to feel safe, strong enough to push the music forward.

Dominant

Maximum tension. The chord that most urgently needs to resolve back to the Tonic. Its pull is unmistakable once you hear it.

Each Degree, Explained

I — Cmaj7 Tonic

This is the home chord — the most stable point in the key. A piece of music can start here, rest here, and end here. When you land on the Imaj7 after a sequence of tension, it feels like a breath of relief. In C major, this is Cmaj7 (C - E - G - B). Everything else in the key is measured relative to this chord.

II — Dm7 Subdominant

The IIm7 is the primary departure chord in jazz. It steps away from home and creates a gentle forward pull. In C major, this is Dm7 (D - F - A - C). You will almost always see this chord moving toward the V7 — it is the first step of the II-V-I, the most important progression in jazz. On its own it sounds like an open question, waiting for an answer.

III — Em7 Tonic

The IIIm7 is a softer, more ambiguous version of home. In C major, Em7 (E - G - B - D) shares three notes with Cmaj7 — which is why it feels stable without feeling as settled as the I chord. Jazz musicians sometimes use it as a substitute for the Imaj7 when they want a slightly more open, less conclusive sound. It is less common than I, III, or VI, but you will find it in turnarounds and as a passing chord.

IV — Fmaj7 Subdominant

The IVmaj7 is a warm, bright departure from home. In C major, Fmaj7 (F - A - C - E) sounds like a step into a slightly different world — not tense, but not at rest either. It is often used to open a phrase or to add color before the Dominant. One important detail: although it is also a Major 7 chord like the Imaj7, the IVmaj7 does not feel like home — it has a floating, unresolved quality that makes it want to move forward.

V — G7 Dominant ★

The V7 is the most powerful chord in the key — the only Dominant 7 that appears naturally in the major scale. In C major, G7 (G - B - D - F) contains a built-in tension that no other diatonic chord has: the interval of a tritone between its 3rd (B) and its 7th (F). These two notes are six semitones apart — the most dissonant interval in Western music — and they urgently want to resolve. B pulls up to C, and F pulls down to E. That resolution lands directly on the Imaj7.

This is why V7 → I is the strongest cadence in tonal music, and why the II-V-I is the backbone of jazz harmony. Every time you hear that satisfying resolution at the end of a phrase, a V7 was the engine behind it.

VI — Am7 Tonic

The VIm7 is a darker, more melancholic version of home. In C major, Am7 (A - C - E - G) shares all its notes with the C major scale — but when it functions as a temporary resting point, it sounds like a different world: the same notes, but heard through a minor lens. This chord is so closely related to the Imaj7 that it has a special name: the relative minor. It is stable enough to feel like home, but colored with a shadow that the Imaj7 does not have. We will explore this relationship fully in the next lesson.

VII — Bm7b5 Dominant

The VIIm7b5 is the most unstable chord in the major key. In C major, Bm7b5 (B - D - F - A) contains the same tritone found in G7 (B and F) — which is why it functions as a Dominant chord and wants to resolve toward the Tonic. In practice, it is less common than the V7 in major keys, but you will encounter it constantly in minor harmony, where it appears as the IIm7b5 chord at the start of a minor II-V-I.

🎹 Play It — Hear the Functions

Play these three progressions slowly on the piano. Listen carefully to how each chord feels:

Tonic only: Cmaj7 → Cmaj7. Complete stillness — no movement, no pull.
Subdominant → Tonic: Fmaj7 → Cmaj7. A gentle departure and return — soft movement.
Dominant → Tonic: G7 → Cmaj7. Feel the tension of G7 dissolve into Cmaj7. That pull is the engine of jazz harmony.

Now play the full II-V-I: Dm7 → G7 → Cmaj7. This is the most important three-chord sequence in jazz — you will use it in every standard you learn.

One Key Insight: Think in Functions, Not Names

The most important habit to develop from this lesson is thinking in functions, not just chord names. When you see a IIm7 chord, don't just think "it's a minor 7 on the 2nd degree" — think "Subdominant, about to move forward." When you see a V7, think "maximum tension — resolution is near." This functional thinking is what allows jazz musicians to instantly understand a new tune, anticipate where progressions are going, and improvise with intention rather than guessing.

Quick Summary

Key takeaways:

Tonic (I, III, VI) — stable, home, no tension
Subdominant (II, IV) — departure, mild tension, movement away from home
Dominant (V, VII) — maximum tension, strong pull back to the Tonic
The V7 is unique: the only Dominant 7 in the major scale, powered by a tritone
The II-V-I (Subdominant → Dominant → Tonic) is the backbone of jazz harmony

What's Next

You noticed that the VIm7 has a special quality — it sounds like a darker version of home. That chord is the gateway to an entire parallel harmonic world called the relative minor:

👉 The Relative Minor

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