The key: what “the song is in G” actually means
The key tells you which chords belong together, and why exactly those.
Adrian10 minupdated
“This song is in G.” For the first few weeks I read that as a note for somebody else, somebody who reads music. When I finally checked what it meant, it turned out to be the most practical sentence on the whole chord sheet. It tells me which chords to expect, which one to end on, and how far to move the capo so that I can sing the thing.
A key is a family of chords
Chords come in families, and the family is called a key. G7 belongs to the C family, D7 to the G family. More formally: a key is seven notes and the seven chords built on them that sound right together. There are twelve major keys, and each one holds three major chords, three minor chords and one diminished.
The second definition is for the ear and gets used more often. The key is the note or the chord the song circles around, sits on and finishes on: coming home and taking your shoes off. The name of the key is the name of that home, so “the song is in G” means: home is G.
Where those seven notes come from
The C family is C, D, E, F, G, A and B. Play them in order on the second string with your index finger alone and count the frets between them. You get two frets, two, one, two, two, two, one. Whole step, whole, half, whole, whole, whole, half. That is the major scale, and the rule ends there.
The pattern never changes, only the starting note does. Starting from G, the same count gives G, A, B, C, D, E and F#, and that single sharp is where the key signature of G comes from. A warning for songbooks from central Europe: German and Polish editions write H where we write B, and their B is our B flat.
Seven chords: 1 4 5 major, 2 3 6 minor, 7 the odd one
On every degree of the scale you stack a triad by taking every other note: the first, the third, the fifth. Seven notes give seven chords, and always in the same order. The first, fourth and fifth are major, the second, third and sixth are minor, and the seventh is diminished and hardly ever shows up in songs. You can skip it and nothing will break.
| key | 1 | 2m | 3m | 4 | 5 | 6m |
|---|---|---|---|---|---|---|
| C | C | Dm | Em | F | G | Am |
| G | G | Am | Bm | C | D | Em |
| D | D | Em | F#m | G | A | Bm |
| A | A | Bm | C#m | D | E | F#m |
| E | E | F#m | G#m | A | B | C#m |
Read this table in rows, not in columns. One row is one song: it will almost certainly use a few chords from that row, and almost certainly none from outside it. If the chord sheet shows a chord that is not in the row, either the song stepped out of the key for a moment, or you have the wrong key.
How to spot the key without counting
The easy clue is the first chord of the song: it works often but not always, so the books hand you a safer one straight away. Check what the song ends on and the chord where your ear feels it can stop playing. That is home, and its name is the name of the key.
In Guitarmatic you do not have to guess: the song page prints the key in the header, next to the time signature. If you want to hear the same song somewhere else, open it and switch the Key, and the app works out which fret the capo goes on.
Why C, G, D, A and E of all keys
These five are called the guitar keys because their chords meet the open grips. A key is friendly to a guitar when it holds most of the shapes you already know: E, Em, A, Am, D, Dm and G. B major no longer fits, which is why almost nobody plays in it round a campfire.
One more convenience, worth knowing at the start. Going from C through G, D and A to E, every next key adds only two new grips and leaves the rest of the row familiar. Five keys is not thirty five new chords, it is about a dozen.
The relative minor: same family, different home
The sixth degree opens a minor scale out of the same notes. A minor holds exactly the notes of C major and exactly the same chords, only home is Am now. That pair is called relative, and it is worth keeping apart from parallel, which means C major and C minor: the same name, different notes.
How to tell a song is minor rather than major: it returns to a minor chord and ends there. God rest you merry gentlemen has Am, Dm, G and F on the sheet and sits down on Am, so its home is Am, although all four chords come out of the C family.
A capo: the same grips, a different key
A capo is a nut you can move. It clamps the strings at a chosen fret and raises everything by as many semitones as the fret number, while the grips stay the same. Put it right next to the fret, not on top of it, and parallel to it, then check the open strings.
| you hold | fret 2 | fret 3 | fret 5 | fret 7 |
|---|---|---|---|---|
| C | D | E♭ | F | G |
| G | A | B♭ | C | D |
| D | E | F | G | A |
| Em | F#m | Gm | Am | Bm |
This is where the trick that gets you round barre chords comes from. A song in C needs an F, and F hurts. Put the capo on the fifth fret, play the grips G, C, D and Em, and the room hears C, F, G and Am. You then hold two things in your head at once: what the fingers do and what the room hears. That is not cheating, it is a second road to the same key.
There is also a drawing that puts every key in order on one wheel, called the circle of fifths. It exists, it is useful for transposing, and it can wait until those five rows of the table are under your fingers.
What confused me
I thought a key was the pitch you sing in, so something that concerned the singer and not me. For a month I read the header of the chord sheet and took nothing from it. A key is not the height of a voice, it is a family of chords: six names you will use for the whole song, and one of them is home.
The second thing I tripped over: C major and A minor are the same notes. I spent a long time hunting for the difference in the chords, and the difference is in where the song sits down. Same family, home moved, different mood.
Do this now
Ear: chords, level 2 (Three pillars in C), key of C.
The exercise plays the tonic first so the ear has something to hold on to, then asks for C, F or G. That is the family this whole guide is about, checked by ear.
Goal: 8 hits out of the 10 questions in a series.
Progressions: pick one and change the key.
The same progression in C, in G and in D. The chord names come out different, the degree numbers stay the same, and that is the only proof this topic needs.
Goal: you recognise the progression by sound in the third key, before you look at the letters.
Play this
two carols, two keys, one ideaJingle Bells is in C and runs on C, F and G: the first, fourth and fifth degree of that key. I Saw Three Ships is in G and needs only G and D, the first and the fifth. Play them one after the other and you hear the same roles wearing different letters.
» I want to play songs, not count degrees.
And you do not have to. But the day a song turns out too high to sing, or an F drops into it, you make that decision in keys, not in grips. Open any song, switch the Key and watch what the app does with the capo: the whole of this theory, done for you in one tap.
Read more
- Beginner Guitar Chords in Theory and PracticeSean Laughton · chapters “The Key To Understanding Chords” and “Wrapping It All Up”It holds the most readable account of keys I know, and next to it the full chord set of the five guitar keys.
- Learning to Play Guitar: Chords, Scales, and SolosColin McAllister · lessons 5, 16 and 18The author walks from the scale to the chords built on it, and gives the capo a whole lesson with an exercise on the third fret.
- Guitar Fretboard MasteryNicolas Carter · chapter “What is a Key?”You get the key defined by ear, and the reason some keys lie well on a guitar while others do not.
- musictheory.net lessonsRicci AdamsThere are free lessons called “The Major Scale”, “Scale Degrees” and “Diatonic Triads”, and you can click through them without a guitar.
- Relative keyWikipediaThe page explains where the naming mess comes from: what English calls relative is called parallel in German, which is why translated books contradict each other.
- CapoWikipediaThe page describes how a capo works and gives the example of two guitarists playing the same thing: one on E, A and B7, the other with a capo on the fourth fret playing C, F and G7.