Harmony and Chords

Musical harmony occurs when two or more notes are played simultaneously. Chords, typically comprising three or more notes, are the primary means of creating harmony. They can be major, conveying brightness or happiness, or minor, often imparting a more somber or introspective tone.

A chord progression is a sequence of chords that creates musical movement and forms the harmonic foundation of a song. One of the most prevalent progressions in popular music is the I–V–vi–IV sequence, used in countless hits like "Let It Be" by The Beatles and "With or Without You" by U2. These Roman numerals represent chords built on different steps of the scale, with uppercase letters (like I, V, and IV) indicating major chords and lowercase letters (like vi) indicating minor chords. In this case, the chords come from the first, fifth, sixth (minor), and fourth steps of the scale.

Another popular variation is the vi–IV–I–V progression, often referred to as the "minor variation" because it begins on the vi chord, giving it a more emotional or melancholic tone. This version appears in songs like “All of Me” by John Legend

The roots of these progressions trace back to Western classical harmony, where certain chord sequences were established as pleasing and stable through centuries of musical practice, especially during the Baroque, Classical, and Romantic periods. The use of tonic (I), dominant (V), and submediant (vi) chords reflects a longstanding harmonic framework designed to create tension and resolution which are essential elements that guide the emotional flow in music.

In the 20th century, as popular music evolved from blues, folk, and early rock, these harmonic patterns were adapted for new genres. The I–V–vi–IV progression, for example, gained prominence because of its versatility and emotional clarity, allowing songwriters to craft memorable melodies over a reliable harmonic base. Its simplicity also makes it accessible to musicians of all levels, contributing to its widespread use in both professional and amateur music-making.

The cultural ubiquity of this chord progression was memorably highlighted by the Australian comedy group Axis of Awesome in their viral 2008 performance “Four Chord Song.” In the medley, they seamlessly wove together dozens of hit songs from genres including pop, rock, and country, all built on the same four-chord sequence. Their performance showed the progression’s versatility and status as a foundational harmonic template that has shaped popular music across multiple decades.

Understanding these harmonic structures deepens our appreciation of how composers use familiar patterns to evoke specific emotions and connect with listeners. The historical grounding of these progressions shows how popular music both inherits and transforms musical traditions, linking contemporary songs to centuries of harmonic practice.