The Progressions Everyone Uses
You now have the three functions and the four endings. That is enough machinery to look at the patterns themselves — and there are surprisingly few of them doing surprisingly much work.
I–V–vi–IV
Four chords, in that order, repeating.
In C major that is C, G, A minor, F. It is the backbone of an enormous number of pop songs across sixty years, to the point where medleys exist purely to demonstrate how many tunes can be sung over the same loop.
Read it functionally and it is easy to see why it works so well:
tonic → dominant → tonic-substitute → subdominant, and then round again
It reaches the tension early, resolves it onto vi instead of I — a deceptive move, which keeps the loop from ever quite closing — and then walks back out through the subdominant to start over. It never ends, which is exactly what a song needs a verse to do.
Start the same four chords on the vi instead and you get vi–IV–I–V, which is the same loop entered at a different door and sounds darker for it. Same chords, different first impression.
ii–V–I
The other essential, and the one jazz is built on.
ii → V → I. Subdominant, dominant, tonic — the three functions in order, with the subdominant played by ii instead of IV.
Why ii and not IV? Because the root moves down a fifth each time: in C major, D to G to C. That is the strongest root motion there is, and doing it twice in a row gives the phrase a momentum that IV–V–I does not have.
It is worth playing both back to back once. IV–V–I steps up and then resolves; ii–V–I falls into place twice. Same functions, different gravity.
The twelve-bar blues
Three chords, twelve bars, one shape:
| Bars | 1–4 | 5–8 | 9–12 |
|---|---|---|---|
| Chords | I I I I | IV IV I I | V IV I V |
Nothing but I, IV and V — the three functions in their plainest form, laid out over a fixed length so that everyone in the room knows where everyone else is without discussing it.
The last bar is the interesting one. Ending on V rather than I is a half cadence, and it is there so the form loops: the twelfth bar is a question that the next chorus answers. Musicians call that bar the turnaround, and it is the reason a blues can go round twenty times without ever sounding like it stopped.
What these three have in common
Every one of them is the same sentence from the first lesson — home, away, tension, home — with something rearranged for effect.
I–V–vi–IV takes the tension early and dodges the ending. ii–V–I compresses the sentence into three chords and drives it with root motion. The blues stretches it over twelve bars and leaves the question hanging at the end.
Learn the sentence and the patterns stop being things to memorise. They are variations on one idea, and you can hear which variation you are in.
Common mistakes to avoid
- Memorising these as chord names. I–V–vi–IV in C is C G Am F, and in G it is G D Em C. The pattern is the numerals; the letters are a detail of which key you happen to be in.
- Thinking the blues needs seventh chords to be a blues. It usually has them, and the form is the twelve bars.
- Treating ii–V–I as a jazz thing. It is in hymns, in Beatles songs, and in almost every standard — jazz just uses it more densely.
Now play
The drill plays a progression with the last chord missing. Most of them are one of the three patterns above, in one key or another.
If you recognise the pattern, you already know the answer. If you do not, fall back on the functions: what job is missing from the sentence?