What is a chord progression?
A chord progression is a sequence of chords heard in time that establishes or moves through a tonal center. In isolation a chord can be recognized by its quality, but it has no role until it's played with other chords. For example, a G major triad is a recognizable three-note sound, but when we play a , it can be a chord that smoothly resolves back to a C tonic. A chord's role in a progression is called its harmonic function.
Harmonic functions are defined relative to a tonic, so a progression keeps its identity in any key. and share no chords, yet they are identifiable as the same progression because every chord relates to its tonic in the same way. Hearing chord progressions means hearing those relations, not letter names of chords, and that's why progressions indicate the root with a Roman numeral rather than a letter name.
What do the Roman numerals mean?
In chord progressions, Roman numerals describe the scale degree of a chord's root relative to the tonic. Uppercase indicates major quality and lowercase means minor. Standard short chord symbols are used for everything else, so vii° indicates a diminished triad, viiø7 is a half-diminished seventh, V7 is a dominant seventh, ii7 or iim7 is a minor seventh, and so on. Read together, a chord's spelling can tell us the root, the quality, and usually the function of the chord, but it says nothing about the key.
Major key
Every diatonic chord has a functional name that describes what it's usually doing harmonically. The tonic (I) is the tonal center. The dominant (V) and leading tone (vii°) create dominant resolutions back to the tonic. The subdominant (IV) and supertonic (ii) prepare the dominant, so they are predominant chords. The mediant (iii) and submediant (vi) share two of their three notes with the tonic and are often used as substitutions for the tonic.
| Numeral | Root | Chord | Function | Listen |
|---|---|---|---|---|
| I | 1 | Major | Tonic | |
| Imaj7 | 1 | Major seventh | Tonic | |
| ii | 2 | Minor | Predominant | |
| iim7 | 2 | Minor seventh | Predominant | |
| iii | 3 | Minor | Tonic substitute | |
| iiim7 | 3 | Minor seventh | Tonic substitute | |
| IV | 4 | Major | Predominant | |
| IVmaj7 | 4 | Major seventh | Predominant | |
| V | 5 | Major | Dominant | |
| V7 | 5 | Dominant seventh | Dominant | |
| vi | 6 | Minor | Tonic substitute | |
| vim7 | 6 | Minor seventh | Tonic substitute | |
| vii° | 7 | Diminished | Dominant | |
| viiø7 | 7 | Half-diminished seventh | Dominant |
Minor key
The fifth and seventh degrees in a minor key each carry two chords, one from natural minor and one from the raised seventh of harmonic minor.
| Numeral | Root | Chord | Function | Listen |
|---|---|---|---|---|
| i | 1 | Minor | Tonic | |
| im7 | 1 | Minor seventh | Tonic | |
| ii° | 2 | Diminished | Predominant | |
| iiø7 | 2 | Half-diminished seventh | Predominant | |
| III | 3 | Major | Tonic substitute | |
| IIImaj7 | 3 | Major seventh | Tonic substitute | |
| iv | 4 | Minor | Predominant | |
| ivm7 | 4 | Minor seventh | Predominant | |
| v | 5 | Minor | Dominant | |
| vm7 | 5 | Minor seventh | Dominant | |
| V | 5 | Major | Dominant | |
| V7 | 5 | Dominant seventh | Dominant | |
| VI | 6 | Major | Tonic substitute or predominant | |
| VImaj7 | 6 | Major seventh | Tonic substitute or predominant | |
| VII | 7 | Major | Subtonic, or dominant of III | |
| VII7 | 7 | Dominant seventh | Subtonic, or dominant of III | |
| vii° | ♯7 | Diminished | Dominant | |
| vii°7 | ♯7 | Diminished seventh | Dominant |
Progressions
We generally name progressions by the sequence of scale degrees that represents their core triads. Because this shorthand focuses on structural movement, sevenths and other specific qualities are usually omitted. A iim7–V7–Imaj7, for example, is referred to as a ii–V–I, or "two, five, one."
| Progression | Common in | Listen |
|---|---|---|
| I–IV–V–I | Folk, hymns, country, blues, and classical | |
| I–V–vi–IV | Pop and rock | |
| vi–IV–I–V | Pop and rock | |
| I–vi–IV–V | 1950s rock and roll and doo-wop | |
| I–vi–ii–V | Jazz and doo-wop turnarounds | |
| ii–V–I | One of the most common resolutions across all Western music | |
| I–IV–I–V | Folk, country, and blues | |
| I–IV–V–IV | Rock and garage rock | |
| I–IV–V–vi | Classical and pop | |
| I–V–vi–iii–IV–I–IV–V | Baroque and pop ballads | |
| IV–vii°–iii–vi–ii–V–I | Baroque sequences and jazz standards | |
| i–iv–V–i | Classical and folk | |
| i–VI–III–VII | Pop, rock, and electronic music | |
| i–VII–VI–V | Flamenco and rock | |
| i–VI–VII–i | Rock, metal, and folk | |
| VI–VII–i | Rock, metal, and film music | |
| ii°–V–i | Classical and jazz | |
| i–iv–VII–III–VI–ii°–V–i | Baroque sequences and jazz standards |
The mechanics of harmony
These recurring shapes are not arbitrary conventions. The major scale contains exactly one tritone, located between its fourth and seventh degrees. The dominant resolution is defined by the tension of . The tritone disappears, the seventh resolves up to the tonic, and the fourth resolves down to the tonic chord's major third. This built-in resolution is why so many progressions organize around getting to V before resolving to I. The leading tone chord vii° is V7 without the root, so it also contains the fourth and seventh, producing the same dominant resolution.
Roots a fifth apart share a chord tone and connect by smooth voice leading, and root motion by descending fifths is a common engine for tonal harmony. V goes to I, ii goes to V, vi goes to ii, and so on out to IV. Almost every progression here is a stretch of that chain, sometimes with a substitution (vi substituting for I, ii for IV, vii° for V) and sometimes with a step motion inserted (IV to V). These patterns are the result of following the resolutions of tendency tones, and centuries of music written that way have trained listeners to expect it.
What is a cadence?
A cadence is a two-chord resolution that concludes a musical phrase. If we think of a chord progression as a sentence, cadences often act similarly to punctuation. An ends V to I, acting as a full stop. A stops on V, leaving the phrase open like a comma. A ends IV to I with no leading tone, creating a gentler stop because nothing in IV tends toward the tonic by a half step. A sets up V and then resolves to vi, acting like a sentence that turns at the last word, keeping two of the tonic's three notes over a different root. Each cadence is defined by what the last two chords do relative to the tonic.
Why raise the seventh in a minor key?
Minor keys inherit the same cadences from major keys with one main complication: the natural minor scale has no leading tone. Its and its . Neither the v nor the VII tends toward the tonic by a half step. A progression like uses the raised seventh degree from harmonic minor to restore the dominant resolution by turning v into V and VII into vii°. That's why minor keys carry two chords on the fifth and seventh degrees, and why a minor-key passage can sometimes sound so different depending on which seventh degree it uses.
How can chord progressions use chords outside the key?
A chord from outside the key is typically borrowed from either the key of the target resolution or a parallel mode. For instance, some progressions use secondary dominants that create dominant resolutions to scale degrees other than the tonic. replaces the minor on ii with II7, referred to as V7/V, or "five of five." Because the second scale degree is a fifth above the fifth scale degree, this creates a temporary dominant resolution to V. Borrowing from a parallel mode, darkens the subdominant by lowering its third, and uses the subtonic of the parallel minor, a sound rock has used for generations. These devices depend on the diatonic frame being securely heard, because their whole effect is the momentary departure from what the listener would otherwise expect.
We already hear this
Harmonic function is not a skill that begins in music theory class. Let's play then and stop. Most people who've grown up hearing Western music, whether or not they have ever named a chord, would hear the second as unfinished, and can usually hum the root of the chord that completes it (Bigand & Poulin-Charronnat, 2006). The same listeners would also hear from outside the key as a mistake, even if they can't explain why. That knowledge is acquired the way the grammar of a first language is acquired, from years of exposure to the same subtle patterns (Tillmann, Bharucha, & Bigand, 2000).
Why do we listen to the bass notes first?
When ear training teaches us to listen to the bass first, it's for a specific acoustic reason. Our ears extract a single fundamental pitch from a chord's combined tones, and a root-position triad with a doubled bass note produces that pitch most clearly (Terhardt, 1974; Parncutt, 1988). The melody of the bass is commonly not just a sequence of scale degrees, but the sequence of roots. A 1–4–5–1 bass line under basic major and minor triads effectively hands us the Roman numerals. The lowest voice is also the easiest to follow because the auditory system naturally groups low frequencies into an independent stream, tracking it separately from the chords above (Bregman, 1990). When the bass plays a note other than the root, it confounds this shortcut, and that's one reason why it's helpful to learn to recognize when chords are inverted.
Which chords get confused?
The confusions in harmonic hearing tend to be systematic, and almost all of them are pairs of chords that share two tones and a function. In major, and share the fourth and sixth scale degrees, and both are predominant. and share the tonic and third scale degree, and both can end a phrase. and both create a dominant resolution. iii shares the third and fifth scale degrees with I and the fifth and seventh degrees with V, so it can be mistaken for either depending on what follows it. Minor confusions typically follow the same pattern.
Progressions in real music
A four-chord stimulus in a fixed rhythm is a distillation. In music, chord progressions are stretched across bars, repeated, decorated with passing chords, and can be reharmonized. Different genres of music also have different harmonic rhythms, but none of that changes the harmonic functions. If we can hear I–V–vi–IV in isolation, we can learn to hear it in a song once the tonic has been found.
Chord progression hearing is a type of functional hearing that builds on the more foundational ear training skills. Hearing that a chord is minor is chord-quality hearing, hearing that its root sits a sixth above the tonic is interval hearing and scale-degree hearing working together, and the scale the chords are drawn from decides which qualities appear on which degrees in the first place. All of these skills can be trained at our ear training hub.