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Chord progressions and harmonic functions (T-S-D)
Four chords, thousands of songs. Meet the most famous progressions (I-IV-V, I-V-vi-IV) and the three functions that explain why music moves forward.
What a chord progression is
A chord progression is a sequence of chords over time. Written in Roman numerals it is independent of key, so the same pattern works in any tonality. A few progressions are so powerful that they drive entire genres.
The most famous progressions
- I - IV - V - I: the foundation of blues, rock and folk.
- I - V - vi - IV: the 'pop progression' behind countless hits.
- ii - V - I: the heart of jazz, the strongest resolution.
- I - vi - IV - V: the sound of classic 1950s pop.
The three harmonic functions
Why do certain chords pull forward? Because they have a function - a role in the drama of tension and release:
- Tonic (T) - I and vi: home, rest, resolution.
- Subdominant (S) - IV and ii: a move away from home, motion.
- Dominant (D) - V and vii°: maximum tension that pushes back to the tonic.
A typical arc is T → S → D → T (e.g. C → F → G → C): you leave home, build tension and return. This is harmonic 'gravity'.
Why the dominant pulls so hard
The V chord contains the leading tone (the 7th degree of the scale), which is just a semitone below the root and 'yearns' to resolve into it. That very semitone gives the V → I progression its irresistible pull toward closure.
Exercise: take I-V-vi-IV in C major (C-G-Am-F) and loop it. Sound familiar? It should. Then try the same pattern in G major (G-D-Em-C) - same feel, different key.
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