> Chords Have Functions
You now know that a major key contains seven diatonic chords. But these chords are not equal. Each has a specific role in creating harmonic movement. This role is called the chord's function.
Think of a story with a beginning, middle, and end. Music works similarly. Some chords establish stability (beginning). Some chords create tension or movement (middle). Some chords demand resolution (leading to the end). This tension-release cycle is what makes music feel satisfying.
Understanding function means understanding why progressions work. Instead of memorizing chord sequences, you learn the logic behind them. This lets you create your own progressions that feel natural.
> The Three Functional Categories
All seven diatonic chords fall into three functional categories: tonic, subdominant, and dominant.
Chords: I, iii, vi
These chords feel stable. They provide resolution and rest. The I chord is the most stable. The iii and vi share notes with I and can substitute for it.
Chords: IV, ii
These chords create gentle movement away from tonic. They suggest something is happening but do not demand immediate resolution. Often lead to dominant.
Chords: V, vii°
These chords create maximum tension. They strongly want to resolve to tonic. The V chord contains the leading tone (7th degree) which pulls toward the root.
> Why V Wants to Go to I
The dominant-to-tonic resolution (V → I) is the most fundamental movement in Western harmony. It feels inevitable, like falling down a hill.
This pull comes from the notes inside the V chord. In C major, the V chord is G major, containing G, B, and D.
Why V → I Feels Inevitable:
- B (leading tone): One half step below C. Strongly pulls upward to the root.
- F (when V7 is used): The 4th degree of the scale, wants to fall to E (the 3rd of I chord).
- G (root of V): A perfect fifth above C. The strongest interval relationship after the octave.
When you play G major and then C major, you are not just changing chords. You are releasing tension that the G chord created. This release is physically satisfying to hear.
> The Basic Progression Flow
Functional harmony follows a general flow: Tonic → Subdominant → Dominant → Tonic. This is not a rule, but a tendency. Most progressions follow some version of this pattern.
Common Progression Patterns:
I → IV → V → I
Tonic → Subdominant → Dominant → Tonic
I → vi → IV → V
Tonic → Tonic substitute → Subdominant → Dominant
ii → V → I
Subdominant → Dominant → Tonic (the most important progression in jazz)
The flow can be interrupted, extended, or inverted for effect. But when you understand the default flow, you understand why deviations sound surprising or creative.
> Famous Progressions Explained
Most popular songs use variations of a few common progressions. Now you can see why they work.
Examples: "Let It Be," "With or Without You," countless others.
Analysis: Starts on rest (I), creates tension (V), moves to tonic substitute (vi) for emotional color, subdominant (IV) provides momentum back to I.
The most basic functional progression. Pure tension and release.
Analysis: Rest → movement → maximum tension → resolution. Simple and effective.
Examples: "Someone Like You," "Apologize"
Analysis: Starting on vi creates immediate emotional weight. The minor color dominates even though the progression is in a major key.
> Substitutions and Variations
Chords within the same functional category can often substitute for each other. This creates variety while maintaining the harmonic logic.
Common Substitutions:
- I → vi or iii:Replace tonic with relative minor or mediant for color.
- IV → ii:Both have subdominant function. ii has a jazzier sound.
- V → vii°:Both create dominant tension, though vii° is more restless.
Try playing I - IV - V - I, then try I - ii - V - I. Both work because ii and IV share the same function. The second version sounds slightly more sophisticated because ii contains a minor quality.
> Common Mistakes
Functions describe tendencies, not laws. Great songs break the expected flow constantly. Understanding function helps you break rules intentionally.
Many guitarists avoid the V because they overuse I-IV or I-vi. The V creates the strongest pull home. Use it.
Delayed resolution creates drama. Sitting on V before going to I builds anticipation. Not every dominant needs instant resolution.
The IV chord leading to I sounds very different than IV leading to V. Same chord, different role in the moment.
> Hearing Function While Playing
The goal is to hear function, not just know it intellectually. When you play a progression, notice:
- Which chords feel like home (tonic function)?
- Which chords create gentle forward movement (subdominant)?
- Which chords demand resolution (dominant)?
This awareness transforms your improvisation. When soloing over a V chord, you know tension is expected. You can emphasize the leading tone, create dissonance, then resolve beautifully when the I chord arrives.
When comping or writing, you can consciously control the emotional arc. Build tension with dominant prolongation. Create space with tonic extensions. Guide the listener through a harmonic journey.
> PRACTICE THIS
Play the progression C - F - G - C (I - IV - V - I in C major). Notice how F creates movement and G creates tension before resolving to C. Then try C - Am - F - G. The Am (vi) adds emotional color while maintaining the same functional flow. Finally, try substituting Dm (ii) for F (IV): C - Am - Dm - G. Hear how the function stays the same but the color changes.
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