Chord progressions
Number the chords of a key with Roman numerals, understand why V pulls back to I, and move a progression like I–V–vi–IV from one key to another.
NUMBERS, NOT LETTERS
Roman numerals
Number the seven chords of a major scale from 1 to 7 with Roman numerals. Capitals mean major, small letters mean minor. Last lesson's family in C major becomes: I = C, ii = Dm, iii = Em, IV = F, V = G, vi = Am, and vii° = Bdim.
A musician says "it's a one, four, five in C" and everyone plays C, F and G. Say "same thing in G" and they all switch, without anyone spelling out a single chord.
The same seven jobs in two keys.
degree: I ii iii IV V vi vii
in C: C Dm Em F G Am Bdim
in G: G Am Bm C D Em F#dimmajor, minor, minor, major, major, minor, diminished
The same order in every major key.Because every major scale has the same step pattern, the chords built on it always come out in this order. Learn it once and it works in all twelve keys.
Check yourself
The band leader says, "One, four, five in G." Which chords does Sara play?
- G, A, B
- G, C, D
- G, Am, Bm
- C, F, G
Show the answer
G, C, D
Yes. In G major the first, fourth and fifth notes are G, C and D, and I, IV and V are all major chords.
THREE JOBS
Home, away and tension
I is home. Songs usually start there and almost always end there. IV is away: a relaxed step out of the house, with no hurry to return. V is tension: it sounds like a question, and the answer it wants is I. A huge amount of music is just these three jobs in different orders.
In C: play C, then F, and it feels like setting off. Play G and hold it, and you are leaning forward. Play C again and you can breathe out.
Leading tone
The seventh note of a major scale, one half step below home. A half step is the shortest distance there is, so this note feels as if it is leaning on the door. The V chord contains it, and that is the main reason V pulls towards I.
In C major the V chord is G B D. B is the leading tone, a half step under C. When G goes to C, the B rises that half step to C and the tension is released.
A sentence that ends with "and…"
Ending on V is like stopping a sentence on "and…". Everyone in the room waits for the rest. Ending on I is the full stop. IV is more like a comma: a pause that could go anywhere. Where the analogy breaks: you need to know a language to feel an unfinished sentence, but people who have never studied a note of music feel an unresolved V just as strongly.
Check yourself
A band playing in the key of C ends its song on a G chord and stops. Most listeners will feel the song has not quite finished.
Show the answer
True
True. G is V in the key of C. It contains B, the leading tone, which is still leaning towards C. Without the final I chord the question has been asked and never answered.
"Twinkle Twinkle" in C, with a simple set of chords.
Each line is two beats.
words chord job
Twin-kle C I
twin-kle C I
lit-tle F IV
star C I
How I F IV
won-der C I
what you G V
are C IOnly three chords: I, IV and V.
The single V comes right before the final I.Home, a step away and back, another step away and back, then one moment of tension on "what you" and the door closes on "are". Most songs are this same story told at greater length.
Check yourself
Omid plays a song with the loop I–V–vi–IV in the key of C: C, G, Am, F. The singer asks for it in G. What does he play?
- G, D, Em, C
- G, D, Am, F
- G, C, D, Em
- D, A, Bm, G
Show the answer
G, D, Em, C
Right. In G major, I is G, V is D, vi is Em and IV is C. Same jobs, new letters.
Two progressions you will hear everywhere
I–IV–V
All three are major chords, so the sound is bright and sturdy. It is the backbone of blues, early rock and roll, folk songs and children's songs. In C: C, F, G.
I–V–vi–IV
Adds vi, the home chord of the relative minor from lesson 6, so a shade of longing slips in. Usually one chord per bar, looping every four bars. In C: C, G, Am, F.
Check yourself
In the key of C, match each chord to its job
Show the answer
- C → I: home, where the song can end
- G → V: tension that wants to resolve
- F → IV: a relaxed step away
- Am → vi: the minor relative of home
Check yourself
Nika is writing a song in the key of C major. Which chords belong to the key?
- Dm (D F A)
- D (D F# A)
- Am (A C E)
- Fm (F Ab C)
- G (G B D)
- E (E G# B)
Show the answer
In the key of C: Dm (D F A), Am (A C E), G (G B D)
Uses a note from outside: D (D F# A), Fm (F Ab C), E (E G# B)
Lesson recap
- Roman numerals name chords by their place in the key: capitals for major, small letters for minor.
- Every major key has the same order: I ii iii IV V vi vii°.
- I is home, IV is a relaxed step away, V is tension that wants to return to I.
- V pulls home because it contains the leading tone, a half step below the home note.
- To change key, keep the numerals and translate them: I–V–vi–IV is C G Am F in C and G D Em C in G.