A chord progression is an ordered sequence of harmonies. The chords matter, but so do their order, duration, bass movement and relationships to the tonal centre. Familiar progressions provide useful starting points rather than compulsory formulas.
Why chord order matters
Compare C–F–G–C with C–Am–F–G. Both use chords from C major, but the first commonly creates a stronger arrival on C, while the second often encourages repetition. Beginning a loop with Am does not by itself put the music in A minor: the tonal centre depends on broader context.
Tonic, predominant and dominant
In a familiar functional major-key setting, I commonly serves as tonic, IV and ii as predominant harmonies and V or V7 as dominant. A ii–V–I in C is Dm–G–C (D–F–A; G–B–D; C–E–G). These categories describe common tendencies, not universal requirements for ambient, rock, modal or electronic music.
Cadences and punctuation
A cadence is a musical gesture of arrival or punctuation, often at a phrase ending. V–I commonly supports an authentic cadence, while IV–I can support a plagal cadence in an appropriate context. The chord names alone do not guarantee a particular cadence: bass, soprano, metre and phrase placement influence what is heard.
Four progression patterns
I–IV–V–I = C–F–G–C; I–vi–IV–V = C–Am–F–G; vi–IV–I–V = Am–F–C–G; ii–V–I = Dm–G–C. These sequences help illustrate harmonic functions and chord order. They may be played as block chords, arpeggios or sustained pads.
Harmonic rhythm
Harmonic rhythm means how frequently the harmony changes. One chord per bar is different from two changes per bar, even if the tempo, metre and keyboard attack pattern remain identical. Longer-held chords can create space; rapid changes can create movement, but neither has a fixed emotional meaning.
Transposition
Roman numerals describe relationships rather than absolute chords. In C major, I–vi–IV–V is C–Am–F–G; in G major, it becomes G–Em–C–D. D major must be D–F♯–A in the new key. The Roman numeral pattern remains constant while the pitches change.
Arranging a progression
Bass notes establish roots or inversions, melodies make chord tones and colour notes audible, and voicings determine how individual notes move. A progression can be transformed without replacing its chords: alter register, harmonic rhythm, chord inversion, articulation or the way it ends.
Part of How Music Works — Volume 2.