Harmony: chord progressions and cadences

Numbering chords with Roman numerals

In the lesson on chords you saw that every major key has a family of seven chords, numbered I to VII. A capital numeral means a major chord, a small numeral means a minor chord, and a small circle (°) means a diminished chord: I ii iii IV V vi vii°.

Numbers are useful because they do not care which key you are in. I – IV – V – I is C, F, G, C in C major, and G, C, D, G in G major. Musicians can say "one, four, five, one" and everybody knows what to play, in any key. Listen: the same journey, starting from two different notes.

• I–IV–V–I in CC, F, G, C.
• I–IV–V–I in GG, C, D, G: the same journey, a little higher.

Three jobs: home, going out, heading home

Chords in a key have jobs, a bit like rooms in a house. The I chord is the tonic: it is home, where everything feels settled. The IV chord is the subdominant: it feels like stepping out of the door. The V chord is the dominant: it feels like being on the way back, wanting to get home.

Other chords can do the same jobs. ii often takes the place of IV, because they share two notes. vi can stand in for I, and vii° acts a lot like V. iii sits somewhere in between. So a very common journey is home → out → heading home → home: I – IV – V – I, or I – ii – V – I.

• Out with IVC – F – G – C: home, out, heading home, home.
• Out with iiC – Dm – G – C: ii does the same job as IV.

Cadences: how a phrase ends

A cadence is the end of a musical phrase, like a comma or a full stop in a sentence. Listen to the same opening finish in four different ways.

A perfect cadence goes V – I, with the tune landing on the home note: a full stop. A plagal cadence goes IV – I. It is softer, and it is also called the Amen cadence, because hymns often sing "A-men" to it. A half cadence stops on V: it sounds like a comma, or a question waiting for an answer. A deceptive cadence (also called an interrupted cadence) sets you up for home with V, then lands on vi instead: a little surprise. In the first and the last example the tune is exactly the same; only the chord underneath changes.

• Perfect (V–I)A full stop: we are home.
• Plagal (IV–I)A soft "Amen" ending.
• Half (ends on V)A comma: it wants to go on.
• Deceptive (V–vi)Same tune as the perfect one, but the chord says "not yet".

Try it: play the half cadence, then hum the note you expect next. Most people hum the home note.

Progressions you will hear everywhere

I – IV – V – I is one of the most basic journeys of all, found in folk songs, hymns and classical music. I – V – vi – IV (C, G, Am, F in C major) is used in a great many pop songs. In jazz, ii – V – I is everywhere: with seventh chords it is Dm7, G7, Cmaj7. Listen to how smoothly it slides, each chord moving only a step to the next.

Some progressions are so famous that they make a whole song shape. The 12-bar blues uses only I, IV and V; you can hear it in the lesson on song form. Pick a key below and try the progressions in other keys.

• I–V–vi–IVC, G, Am, F: a pop favourite.
• ii–V–IDm7, G7, Cmaj7: the jazz way home.

In minor keys, V often turns major

In A minor, the chords built only from the natural minor scale give a minor v: E minor (E G B). It works, but it does not pull very hard towards home.

So musicians usually raise the seventh note of the scale by a half step, from G to G♯. This is the harmonic minor scale from the lesson on scales. Now the v chord becomes a major V (E G♯ B), and G♯ sits just a half step below the home note A, leaning right into it. Listen to the difference: the major V sounds as if it really wants to go home.

• Am – Em – AmMinor v: a gentle way home.
• Am – E – AmMajor V with G♯: a strong pull home.

Your turn: make a journey

You now know enough to write your own chord progression. Start on I so the listener knows where home is. Go out with IV or ii, head back with V, and choose your ending: a full stop with I, a comma with V, or a surprise with vi.

There are no wrong answers, only different journeys. Many songs simply repeat four chords again and again and let the melody tell the story.

Try it: with the progression player or any keyboard, play I – vi – ii – V and then I. Does the last chord feel like coming home?

Keep exploring

• ChordsA chord is notes played at the same time. Build a chord in three steps, hear major and minor, and see which chords belong together in a key.
• Chord symbolsTurn a chord around, see why players do it, and learn to read C/E, Cm7, Csus4, Cadd9 and other symbols on a song sheet.
• ScalesA scale is a set of notes climbing step by step, built from a simple recipe. Pick any starting note and hear major, minor, pentatonic, blues and more.
• Song formSongs are built from parts that come back. Learn verse, chorus and bridge, how musicians name parts with letters, and the 12-bar blues.
• MelodyA tune is a line of notes with a shape. Hear steps and leaps, motifs, phrases, question and answer, then write one.