Keys and How Songs Work
What You’ll Learn
Section titled “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 Concept Explained
Section titled “The Concept Explained”What Is a Key?
Section titled “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.
Chords Built from a Major Scale
Section titled “Chords Built from a Major Scale”Every major scale produces a set of seven chords, one built on each scale degree. 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 |
| vii° | diminished | B° | F#° |
Convention: uppercase Roman numerals = major, lowercase = minor, ° = diminished.
This pattern — Major, minor, minor, Major, Major, minor, diminished — is the same in every major key. Only the note names change.
For now, focus on the most important chords: I, IV, V, and vi. These four chords are used in the vast majority of popular songs, including many in this course.
The “Four-Chord Song”
Section titled “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. In Session 10, you play “About a Girl” by Nirvana (Em-G) and “Knockin’ on Heaven’s Door” by Bob Dylan (G-D-Am), both of which use chords from the key of G.
Minor Keys
Section titled “Minor Keys”Songs can also be in a minor key. A minor key uses the notes of a minor scale and has a minor chord as its tonal centre. The most common minor key for guitar is A minor, because the Am chord uses open strings and the Am pentatonic scale sits perfectly in open position.
The chords in a minor key follow a different pattern:
| Degree | Chord Type | In Key of Am |
|---|---|---|
| i | minor | Am |
| ii° | diminished | B° |
| 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.
Relative Major and Minor
Section titled “Relative Major and Minor”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.
How This Helps You Learn Songs
Section titled “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. “Ye Shaam Mastani” and “Pal Pal Dil Ke Paas” (Session 11) use chords from one key family, and once you know the key, the chord changes become predictable rather than random.
Key Signatures
Section titled “Key Signatures”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 become more important when you begin reading standard notation (see Reading Standard Notation).
On Your Guitar
Section titled “On Your Guitar”Exercise 1: Play the I-IV-V-I Progression in G
Section titled “Exercise 1: Play the I-IV-V-I Progression in G”Play these four chords in sequence, four strums each, at a comfortable tempo:
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
Section titled “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.
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.
Exercise 3: A Minor Progression
Section titled “Exercise 3: A Minor Progression”Play: Am - G - C - Em, four strums each:
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
Section titled “Exercise 4: Identify the Key by Ear”Play the G-D-Em-C progression and stop on G. That feels like the ending, the resting point. Now play the same chords but stop on Em instead. 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.
Try: play Am-G-C, and stop on Am. Now stop on C. Am feels more “at rest” — the song is in A minor.
Quick Quiz
Section titled “Quick Quiz”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”?
Answers
Section titled “Answers”- 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.
- Major.
- I = C, IV = F, V = G.
- 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.
- The G chord (the I chord). It is the tonal centre — the chord that feels stable and resolved.
Key Takeaway
Section titled “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.