Stop 6 of 7
Keys and the circle of fifths
Key signatures, relatives and the map that orders every key.
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Stop 6 of 7
Key signatures, relatives and the map that orders every key.
When someone says "this song is in G", they're talking about its key: the neighbourhood of notes and chords where the music lives and the home it returns to. In this stop you connect the major scale with keys, learn to read the key signature at the start of every staff and discover the map that orders all twelve keys: the circle of fifths. For a guitarist it's much more than theory: it explains why certain chords always turn up together.
Listen to this progression. Then listen to the same one, starting on a different chord:
They sound "the same", with the same feeling of leaving home and coming back, but the second is higher. The music is the same; the home has changed. The first is in the of G major: it uses the notes of the G major scale and rests on G. The second is in D major.
If a song is in D major, every F and every C will be sharp. Writing a ♯ before each one would be exhausting, so they're written once, at the start of every line, right after the clef. That's the .
Look at the staff: there's no ♯ in front of any note, but at the start there are two: on the F line and in the C space. They mean "every F and every C is sharp, in any octave, until told otherwise". Hear how F♯ and C♯ sound even though they're not written next to the note.
Each major key has a different key signature. These are the ones most used on guitar:
| Key | Accidentals | Altered notes |
|---|---|---|
| C major | none | — |
| G major | 1 ♯ | F♯ |
| D major | 2 ♯ | F♯ C♯ |
| A major | 3 ♯ | F♯ C♯ G♯ |
| E major | 4 ♯ | F♯ C♯ G♯ D♯ |
| F major | 1 ♭ | B♭ |
| B♭ major | 2 ♭ | B♭ E♭ |
| E♭ major | 3 ♭ | B♭ E♭ A♭ |
Notice that the "guitar keys" (G, D, A, E) are sharp keys: they match the open strings. Wind instruments (trumpet, sax) prefer flat keys.
Sharps don't appear at random: always in the same order, and each key adds a new one at the end of the previous list.
Sharps: F · C · G · D · A · E · B
Flats: B · E · A · D · G · C · F
The order of flats is the order of sharps backwards. With them you have two tricks for reading any key signature:
Now look at the sequence of sharp keys: C, G, D, A, E… Each tonic is seven half steps above the previous one: a fifth. And each step adds a sharp. If you place the twelve keys in a circle in that order, you get the :
C major (0)
C major
I C · ii Dm · iii Em · IV F · V G · vi Am · vii° Bdim
Press a key to see its diatonic chords. Neighbouring keys share almost all their notes.
Why does it work? Remember the two tetrachords of the major scale: the upper half of C major (G-A-B-C) is the lower half of G major. Going from C to G you only need to change one note: F rises to F♯ so that degree 7 sits a half step below the new tonic.
And you already know the fifth with your fingers: it's the interval of your power chords. Listen to the fifth, then take a trip round the circle with power chords:
Play the C major scale, but starting and ending on A. The same notes, no accidentals at all, now sound sad, darker:
C major and A minor share all their notes and the same key signature. They are . Hear the difference in "home":
To find the relative minor of any major key, go to its 6th degree, or go down three half steps (three frets) from the tonic: G major → E minor; D major → B minor; F major → D minor. On the circle, each major key has its relative minor next to it, on the inner ring.
The A (A, C, D, E, G) uses five notes of C major. That's why, when you improvise with box 1 at the 5th fret over a song in C major, almost everything fits: you're playing notes of the relative key. You'll explore this in depth in The Peaks of Expression with the major pentatonic.
The circle isn't just a drawing: it tells you which chords get along. In any major key, the three main major chords are the tonic and its two neighbours on the circle:
| Key | Left neighbour (IV) | Tonic (I) | Right neighbour (V) |
|---|---|---|---|
| G major | C | G | D |
| D major | G | D | A |
| A major | D | A | E |
Does the last row ring a bell? It's your in A: A7, D7 and E7, three neighbours on the circle. Now you know why those three chords work together.
Goal: Play the twelve power chords of the circle in order (C, G, D, A, E, B, F♯, C♯, A♭, E♭, B♭, F), two beats each, at 80 BPM, saying each name.
Look at the key signature of the A major tune: three sharps, the last one is G♯, so the tonic is A. Play the scale with the movable shape from string 6, fret 5, and then the tune with those same notes (it will sound an octave lower than the audio: it's the same tune). Repeat with the D major tune using the shape from string 6, fret 10.
Goal: Name the key of the A major tune and play it with the movable major-scale shape (tonic on string 6, fret 5) without mistakes.
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