Keys and How Songs Work

When to read this: Session 19 assigns this handout. Read it after the session: the reading is not part of the session’s 50 minutes. Read from “What Is a Key?” to the end of “How This Helps You Learn Songs” (about 10 minutes). The sections headed “Going Further” are optional.

What You’ll Learn

When musicians say a song is “in the key of G” or “in A minor,” they are describing the set of notes and chords the song uses. A key is like a home base — it tells you which notes belong to the song and which chord feels like “home.” This handout explains what keys are, how chords are built within a key, why certain chord progressions sound natural, and how this knowledge helps you learn songs faster on your guitar.

The main part of this handout is about four chords, called I, IV, V and vi, in the keys of G, C and A. The sections headed “Going Further” are optional.

The Concept Explained

What Is a Key?

A key is a group of notes that a song uses, based on a major or minor scale. When a song is “in the key of C major,” it primarily uses the seven notes of the C major scale (C-D-E-F-G-A-B) and the chords built from those notes.

The key also defines a tonal centre — the note and chord that feel like home, like rest, like the ending. In the key of C major, the C chord feels like home. The song may wander through other chords, but it resolves back to C.

The I, IV, V and vi Chords

Every key has a family of chords that belong to it. They are numbered by counting letter names up from the home note, and the numbers are written as Roman numerals.

Count letter names up from A: A is 1, B is 2, C is 3, D is 4, E is 5. The chords on 1, 4 and 5 are A, D and E. That is all I, IV and V mean here. Count one letter further, to 6, and you reach the vi chord.

Numeral	Built on	Chord Type
I	the 1st note (the home note)	Major
IV	the 4th note	Major
V	the 5th note	Major
vi	the 6th note	minor

Convention: uppercase Roman numerals = major, lowercase = minor.

Here are the four chords in the three keys this course uses most:

Key	I	IV	V	vi
G major	G	C	D	Em
C major	C	F	G	Am
A major	A	D	E	F#m

You learn every chord in this table during the course except F#m, which this course does not teach. (The F is the simplified F chord from Session 17. In the key of A the 6th note is F#, not F, which is why its vi chord is F#m.)

These four chords are used in the vast majority of popular songs, including many in this course.

The “Four-Chord Song”

An enormous number of songs use some combination of the I, V, vi, and IV chords. In the key of G major:

Numeral	Chord	Role
I	G	Home — feels stable, resolved
V	D	Tension — wants to move back to I
vi	Em	Emotional — adds depth, often in verses
IV	C	Lift — creates movement, often before V

The progression G - D - Em - C (I - V - vi - IV) or variations of it appears in hundreds of songs. The four-chord progression you practise in Session 11, G - Em - C - D (I - vi - IV - V), is one of those variations: the same four chords in a different order.

Two songs from Session 10 draw on this family of chords. “Knockin’ on Heaven’s Door” by Bob Dylan is in the key of G major, and its chords are G, D, Am and C. The verse of “About a Girl” by Nirvana moves between Em and G; the song is in E minor, a key that shares its chords with G major (see “Going Further: Relative Major and Minor (Optional)”).

The Progressions You Play in This Course

Here is each progression from the sessions, with its chord numbers.

The 12-bar blues in A (Session 8): I, IV and V. In the key of A, I = A, IV = D and V = E. The twelve measures are:

| A  | A  | A  | A  |
| D  | D  | A  | A  |
| E  | D  | A  | E  |

In chord numbers, the same twelve measures are:

| I  | I  | I  | I  |
| IV | IV | I  | I  |
| V  | IV | I  | V  |

Because the pattern is written in numbers, it works in any key: put that key’s I, IV and V chords into the same twelve measures.

The four-chord progression (Session 11): I - vi - IV - V in G. G - Em - C - D, one measure each.

“Ye Shaam Mastani” (Session 11): I, vi, IV and V in G. The refrain chart uses the same four chords, G, Em, C and D. Its first line is G - Em - G - G (I - vi - I - I) and its second line is C - D - G - G (IV - V - I - I). Both lines come home to G, the I chord.

“Pal Pal Dil Ke Paas” (Session 11): I, vi, ii and V in G. The refrain chart is G - Em - Am - D - G - G (I - vi - ii - V - I - I). Am is the ii chord: the minor chord built on the 2nd note of the key of G, which is A. Again the line ends at home on G.

The 12-bar blues in A minor (Session 22): i, iv and v. This is the same twelve-measure pattern with Am, Dm and Em in place of A, D and E. The home chord is now a minor chord, so the piece is in a minor key and all three numerals are written in lowercase: i = Am, iv = Dm, v = Em.

How This Helps You Learn Songs

When you know a song’s key, you can predict which chords will appear. If someone says “this song is in G,” you immediately know the likely chords are G, C, D, Em, and Am. You do not need to memorise each song’s chord chart from scratch — the key tells you the family of chords the song draws from.

This also helps with the Hindi film songs in the course. The charts for “Ye Shaam Mastani” and “Pal Pal Dil Ke Paas” (Session 11) both use chords from the key of G, and once you know the key, the chord changes become predictable rather than random.

Going Further: All the Chords of a Major Key (Optional)

Every major scale produces a chord on each of its notes. These are called diatonic chords (diatonic means “belonging to the key”). The pattern of major and minor chords is the same for every major key:

Degree	Chord Type	In Key of C	In Key of G
I	Major	C	G
ii	minor	Dm	Am
iii	minor	Em	Bm
IV	Major	F	C
V	Major	G	D
vi	minor	Am	Em

This pattern — Major, minor, minor, Major, Major, minor — is the same in every major key. Only the note names change. (Bm is not taught in this course. There is also a chord on the 7th note of the scale. It is a tense-sounding kind called a diminished chord, which this course does not use, so it is left out of the table.)

Going Further: Minor Keys (Optional)

Songs can also be in a minor key. A minor key has a minor chord as its tonal centre and uses the notes of a minor scale. The A natural minor scale is A B C D E F G: the same notes as C major, starting from A. The most common minor key for guitar is A minor, because the Am chord uses open strings and the Am pentatonic scale sits in open position.

The chords in a minor key follow a different pattern:

Degree	Chord Type	In Key of Am
i	minor	Am
III	Major	C
iv	minor	Dm
v	minor	Em
VI	Major	F
VII	Major	G

A common Am progression: Am - G - F - Em — used in countless rock songs.

Going Further: Relative Major and Minor (Optional)

Every major key has a relative minor that shares exactly the same notes and chords, just with a different “home” chord:

• C major and A minor are relatives — same notes (C-D-E-F-G-A-B), same chords, but C major feels like home at C, while A minor feels like home at Am
• G major and E minor are relatives — same notes (G-A-B-C-D-E-F#), different home chord

This is why the chord progressions in this course often mix major and minor chord names — they frequently share a key.

Going Further: Key Signatures (Optional)

A key signature is a shorthand that tells you which notes are sharped or flatted throughout a piece. Instead of writing # or b before every affected note, the key signature states it once at the beginning:

Key	Sharps/Flats
C major / A minor	None
G major / E minor	F#
D major / B minor	F#, C#
F major / D minor	Bb

For this course, you primarily work in C major (no sharps/flats), G major (one sharp: F#), A minor, and E minor. Key signatures matter when you read standard notation. The notes and melodies in Reading Standard Notation all use C major or A minor, which have no sharps or flats, so you will not need a key signature there.

On Your Guitar

Exercise 1: Play the I-IV-V-I Progression in G

Play these four chords in sequence, four strums each, at a comfortable tempo:

G (I)

OOO

2

3

4

EADGBe

C (IV)

XOO

1

2

3

EADGBe

D (V)

XXO

1

2

3

EADGBe

G (I)

OOO

2

3

4

EADGBe

G:

• Finger 2 (middle): string 5 (A), fret 2
• Finger 3 (ring): string 6 (low E), fret 3
• Finger 4 (little finger): string 1 (high e), fret 3
• Strings 4, 3 and 2 are played open
• Strum all six strings

D:

• Finger 1 (index): string 3 (G), fret 2
• Finger 2 (middle): string 1 (high e), fret 2
• Finger 3 (ring): string 2 (B), fret 3
• String 4 (D) is played open
• Do not play strings 6 and 5
• Strum strings 4 to 1 (four strings)

Listen to how D (the V chord) creates tension, and G (the I chord) at the end feels like “coming home.” That pull from V to I is the strongest resolution in music.

Exercise 2: The I-V-vi-IV Progression

Now add Em (the vi chord) for the famous four-chord pattern:

Play: G - D - Em - C, four strums each, repeating. Use a simple down-down-down-down strumming pattern.

G

OOO

2

3

4

EADGBe

D

XXO

1

2

3

EADGBe

Em

OOOO

2

3

EADGBe

C

XOO

1

2

3

EADGBe

Loop this four or five times. You are playing a chord progression that works under hundreds of well-known songs. Every chord belongs to the key of G major.

Then play the same four chords in the Session 11 order, G - Em - C - D (I - vi - IV - V), four strums each.

Exercise 3: A Minor Progression

This exercise goes with “Going Further: Minor Keys (Optional)”. Play: Am - G - C - Em, four strums each:

Am

XOO

1

2

3

EADGBe

G

OOO

2

3

4

EADGBe

C

XOO

1

2

3

EADGBe

Em

OOOO

2

3

EADGBe

All four chords belong to both C major and A minor (relative keys). Starting on Am gives a darker, more emotional feel. Starting on G or C gives a brighter feel — same notes, different mood depending on which chord feels like home.

Exercise 4: Identify the Key by Ear

Play G - D - Em - C, then G once more, and stop on that G. That feels like the ending, the resting point. Now play the same chords but stop on Em instead (G - D - Em). Notice how Em does not feel as final — you want to hear more. The chord that feels like the natural ending is the home chord, which tells you the key.

Play Am - G - Em - Am and stop on the last Am. Then play C - G - Am - C and stop on the last C. When chords are shared by two related keys, home is the chord the progression starts from, keeps returning to and ends on.

Quick Quiz

Question 4 goes with the “Going Further” sections.

1. If a song is “in the key of G major,” what does that tell you?

2. In any major key, the chord built on the I, IV, and V degrees are what type?

3. What are the I, IV, and V chords in the key of C major?

4. C major and A minor are “relative” keys. What does that mean?

5. In the key of G major, which chord feels like “home”?

6. Name the I, IV and V chords in the key of A.

Answers

1. The song primarily uses the seven notes of the G major scale (G-A-B-C-D-E-F#) and the chords built from them.
2. Major.
3. I = C, IV = F, V = G.
4. They share exactly the same notes and chords, but have different tonal centres (different “home” chords). C major resolves to C; A minor resolves to Am.
5. The G chord (the I chord). It is the tonal centre — the chord that feels stable and resolved.
6. I = A, IV = D, V = E. These are the three chords of the 12-bar blues in A.

Key Takeaway

A key is a family of notes and chords built from one scale. Knowing the key of a song tells you which chords to expect and which note is “home.” The I, IV, V, and vi chords cover the vast majority of popular songs. Once you recognise these patterns, learning new songs becomes faster because you are not memorising random chords — you are hearing a system that repeats across all music.