Stop 5 of 5
Progressions in any key
I–IV–V, I–V–vi–IV and the number system.
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Stop 5 of 5
I–IV–V, I–V–vi–IV and the number system.
You can move shapes now. Time to use them for what really matters: playing progressions — the chord sequences that hold up almost all popular music — in whatever key the song, the singer or the rest of the band asks for. For that you need to think in numbers instead of names. Once you do, four progressions will let you accompany hundreds of songs in any key.
Each major key has seven "home" chords, one on each note of its scale. Roman numerals name them by position, not by note: upper case for major chords, lower case for minor ones.
| Degree | I | ii | iii | IV | V | vi | vii° |
|---|---|---|---|---|---|---|---|
| Quality | major | minor | minor | major | major | minor | diminished |
| In G | G | Am | Bm | C | D | Em | F♯dim |
| In C | C | Dm | Em | F | G | Am | Bdim |
| In A | A | Bm | C♯m | D | E | F♯m | G♯dim |
The pattern of qualities — major, minor, minor, major, major, minor, diminished — is the same in every major key. We'll leave the diminished seventh degree for the harmony stage; the progressions at this stop use the other six.
Here's the big reward of movable shapes: the chords of a key always sit in the same relative position around the I. If the I is an E shape, the other degrees are laid out like this:
String 6, Fret 3: G2 · 1 · Scale tone
And if the I is an A shape, the map flips:
String 5, Fret 3: C3 · 1 · Scale tone
Move the I to any fret and the map travels with it. You no longer need to work out what the IV of A♭ is: put down the A♭ barre (E shape, fret 4) and the IV is at the same fret, as an A shape.
The sixth and fifth strings are tuned five semitones apart, and the IV of a key is exactly five semitones above the I. So at the same fret, the fifth string gives you the IV of whatever is on the sixth. The V is two semitones above the IV: two more frets. The ii is two semitones above the I, and the vi nine semitones above (or three below). Since all these distances are fixed in every major key, so are the positions on the map.
This is the progression of the : blues, rock and roll, folk and country. With the map, in the key of A your hand barely moves:
And with the I as an A shape, for example in C:
These two four-chord progressions sit behind a huge number of pop songs from recent decades. They sound different because they change the order: I–V–vi–IV pushes forward with energy and starts again; I–vi–IV–V has a more nostalgic air, like a 1950s ballad.
Play the same four chords of I–V–vi–IV but start on the vi (vi–IV–I–V: Em – C – G – D), and the music changes character: the ear takes the minor chord as its resting point and everything sounds darker. That's the minor key peeking through with the same chords. Try it with the backing: same fingers, different emotion.
One progression rules jazz and turns up in many other styles: ii–V–I. It's usually played with seventh chords, and barre chords make it easy. In C:
Notice how little your hand moves: from ii to V you drop two frets and change string; from V to I you stay at the same fret. The tension of G7 resolves into C like a question finding its answer. For now, treat it as a taster: you'll study it in depth in later stages.
Session musicians needed a way to write progressions that worked in any key, so a singer could ask for "one step up" without anything being rewritten. The answer was the : degrees are written as ordinary numbers, and minor chords get an "m" (or a minus sign).
| Roman | I | ii | iii | IV | V | vi |
|---|---|---|---|---|---|---|
| Nashville | 1 | 2m | 3m | 4 | 5 | 6m |
An eight-bar Nashville chart looks like this. Each number is one bar:
1 · 4 · 6m · 5 · 1 · 4 · 5 · 1
If the band decides to play it in D, it sounds like this:
And if the singer prefers F, you change barre and the chart stays the same:
| Key | I | V | vi | IV |
|---|---|---|---|---|
| A | E, fr. 5 | A, fr. 7 | E minor, fr. 2 | A, fr. 5 |
| C | A, fr. 3 | E, fr. 3 | E minor, fr. 5 | E, fr. 1 |
| E♭ | A, fr. 6 | E, fr. 6 | E minor, fr. 8 | E, fr. 4 |
| B♭ | A, fr. 1 | E, fr. 1 | E minor, fr. 3 | A, fr. 6 |
In B♭ the IV should be an E shape two frets below fret 1… which doesn't exist! So you play it as an A shape five frets higher (fret 6). There's always a plan B.
Goal: Play I–V–vi–IV in A, C, E flat and B flat, two rounds each, without stopping between keys.
Play the chart from the previous scene first in D (I as an A shape, fret 5) and then in F (I as an E shape, fret 1). Use the two backings above. Finally, pick a new key yourself.
Goal: Play the 1–4–6m–5–1–4–5–1 chart in D and in F without writing down the chord names.
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