The Grammar of Musical Harmony
Chord progressions are the sentences of music — sequences of chords that create tension, movement, and resolution. Just as language has grammar rules, harmony has principles that composers have followed (and broken) for centuries. The Roman numeral system assigns each chord a number based on its scale degree: I is the tonic (home), V is the dominant (tension), and IV is the subdominant (departure).
Why Some Progressions Dominate Pop Music
The I-V-vi-IV progression appears in an astonishing number of hit songs — from The Beatles' 'Let It Be' to Adele's 'Someone Like You'. Its power lies in its emotional arc: the major tonic establishes home, the dominant creates energy, the relative minor adds emotional depth, and the subdominant gently returns toward home. This simulator lets you see the harmonic tension rise and fall through each chord change.
Voice Leading: The Hidden Art
Great harmony is not just about choosing the right chords — it's about how individual notes move between them. Voice leading, perfected by Bach, minimizes the distance each voice travels between chords. When a soprano note can stay the same (a common tone), it does. When it must move, it moves by step rather than leap. The result is a seamless, flowing texture that the listener feels but rarely notices consciously.
From Classical Cadences to Jazz ii-V-I
The strongest harmonic motion in Western music is the authentic cadence: V resolving to I. This dominant-to-tonic pull drives everything from Beethoven symphonies to blues turnarounds. Jazz musicians extended this by adding the ii chord before the V, creating the ii-V-I — the most important progression in jazz. This simulator visualizes how tension builds and resolves across these fundamental patterns.