What is a Chord? Structure, Intervals, and Types
Learn the fundamental structure of guitar chords and why they work the way they do
What is a Chord?
A chord is three or more different musical notes played simultaneously. When you strum multiple strings on your guitar together, you're creating a chord.
But here's the key insight: chords aren't random combinations of notes. They follow specific mathematical relationships called intervals that create harmony. (If you're not familiar with musical notes, check out our Beginner's Guide to Notes on the Guitar.)
The Structure of Chords: It's All About Intervals
Understanding Intervals
An interval is the distance between two notes, measured in semitones. On guitar, one semitone equals one fret - so when we say "4 semitones," that's the same as "4 frets" on your guitar neck.
Chromatic Scale Reference
Below is a visual reference of the chromatic scale (one octave plus the next A). Use the fretboard diagram below to see how these notes appear on each guitar string.
Guitar String Fretboard
Click on a string button to see the notes on the first 12 frets of that string.
First 12 frets of the A string:
Click a string above to view its notes on the first 12 frets.
Important Note:
It's important to note that chords must be played with one note per string. While this may seem obvious, it's a key concept for beginners to understand. On guitar, chord notes are spread across multiple strings rather than being played in sequence on one string.
Octaves: Guitar chords often use the same notes in different octaves (higher or lower versions of the same note). For example, a C major chord might include a low C on the 5th string and a high C on the 2nd string - both are still "C" notes, just in different octaves. The 4-semitone relationship between C and E exists regardless of which octave each note is played in.
Example: C Major Chord
- C (root note)
- E (4 semitones above C)
- G (3 semitones above E, 7 semitones above C)
The distances between these notes (4 semitones, then 3 semitones) create the specific sound we recognize as a "major" chord.
Chord Formulas: The Universal Pattern
Here's where it gets interesting: all chords of the same type use identical interval patterns, regardless of which note you start on.
Major Chord Formula
Root + 4 semitones + 3 semitones
Examples:
C Major Chord:
| Note | C | C# | D | D# | E | F | F# | G | G# | A | A# | B | C |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Semitones from C | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
Root: C (0), Major 3rd: E (4 semitones), Perfect 5th: G (7 semitones)
G Major Chord:
| Note | G | G# | A | A# | B | C | C# | D | D# | E | F | F# | G |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Semitones from G | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
Root: G (0), Major 3rd: B (4 semitones), Perfect 5th: D (7 semitones)
A Major Chord:
| Note | A | A# | B | C | C# | D | D# | E | F | F# | G | G# | A |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Semitones from A | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
Root: A (0), Major 3rd: C# (4 semitones), Perfect 5th: E (7 semitones)
Every major chord follows this exact same pattern - only the starting note changes.
Minor Chord Formula
Root + 3 semitones + 4 semitones
C Major vs C Minor Comparison:
C Major Chord:
| Note | C | C# | D | D# | E | F | F# | G | G# | A | A# | B | C |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Semitones from C | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
Root: C (0), Major 3rd: E (4 semitones), Perfect 5th: G (7 semitones)
C Minor Chord:
| Note | C | C# | D | Eb | E | F | F# | G | G# | A | A# | B | C |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Semitones from C | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
Root: C (0), Minor 3rd: Eb (3 semitones), Perfect 5th: G (7 semitones)
Notice how minor chords flip the interval pattern compared to major chords (3+4 instead of 4+3).
Easy Way to Figure Out Notes in Any Chord
Step 1: Know the Chord Formula
For major chords, the formula is 1 - 3 - 5. This means you need the 1st, 3rd, and 5th notes counting from your starting note.
Step 2: Find the Root Note
The chord name tells you the starting note. For example:
- C major (or just "C") starts on the note C
- G major (or just "G") starts on the note G
- Convention: Major chords are written as just the letter (C, G, A) without the word "major"
Step 3: Count Using the Musical Alphabet
Label your starting note as "1" and count up using letters.
Example: C Major Chord
- (1) C
- (2) D
- (3) E ← This is your 3rd
- (4) F
- (5) G ← This is your 5th
Result: C major chord = C, E, G
Example: G Major Chord
- (1) G
- (2) A
- (3) B ← This is your 3rd
- (4) C
- (5) D ← This is your 5th
Result: G major chord = G, B, D
Important: The musical alphabet goes A-B-C-D-E-F-G, then repeats. If you count past G, continue with A, B, C, etc.
When You Need Sharps or Flats
Sometimes counting by letters isn't enough, and you need to account for correct spelling of notes.
Example: C Minor Chord
Using the 1-3-5 formula:
- (1) C
- (2) D
- (3) E ← But minor chords use a "flattened 3rd"
Since we counted to E for the 3rd, a flattened 3rd becomes Eb (not D#, even though they're the same pitch). We use Eb because it maintains the correct alphabetical spelling - we need some version of "E" for the 3rd note.
Example: D Major
The chord D major needs the notes D, F#, A (not D, F, A - that would be D minor).
Why F# instead of Gb? Count 4 semitones from D on the chromatic scale:
D → D# → E → F → F# (4 semitones)
We use F# (not Gb) because when counting 1-2-3 from D, we get D-E-F. The 3rd should be some version of "F," so we use F#.
Musical Spelling Rule:
Use the letter name that corresponds to the chord formula position, then add sharps or flats as needed.
Quick Reference: Which Notes Have Sharps/Flats Between Them?
Remember these two pairs: B-C and E-F
- B and C are next to each other (no sharp/flat between)
- E and F are next to each other (no sharp/flat between)
- All other letter pairs have a sharp/flat between them
Sharp vs Flat Naming:
The same pitch can have two names depending on context:
- Sharp (#) uses the letter name before it: C# comes after C
- Flat (b) uses the letter name above it: Db comes before D
Examples:
- The note between C and D can be called C# (C-sharp) or Db (D-flat)
- The note between F and G can be called F# (F-sharp) or Gb (G-flat)
- The note between G and A can be called G# (G-sharp) or Ab (A-flat)
Which name to use? Follow the alphabetical spelling rule from the chord formula - use whichever version maintains the correct letter sequence for your chord.
Common Chord Types and Their Formulas
Major Chords
- Formula: Root + 4 + 3 semitones
- Sound: Bright, happy, stable
- Examples: C, G, D, A, E, F
Minor Chords
- Formula: Root + 3 + 4 semitones
- Sound: Sad, dark, emotional
- Examples: Am, Em, Dm, Bm, Fm
Dominant 7th Chords
- Formula: Root + 4 + 3 + 3 semitones (adds a 7th)
- Sound: Bluesy, unresolved, wanting to move
- Examples: G7, C7, D7, A7
Minor 7th Chords
- Formula: Root + 3 + 4 + 3 semitones
- Sound: Jazzy, smooth, sophisticated
- Examples: Am7, Em7, Dm7
Chord Shapes: Open and Moveable
Understanding chord structure is only half the story. How you play chords on the guitar depends on their ergonomic design - how they fit under your fingers.
Open Chords
Chords that use open (unfretted) strings mixed with fretted notes. Played in the first few frets with unique finger patterns that cannot be easily moved to different keys.
Moveable Chord Shapes
Chord patterns with no open strings that can be moved up and down the neck to play different chords. The same fingering pattern works in any position, allowing you to play any chord with just a few learned shapes. Barre chords are the most common type of moveable chord shape.
Building Your Understanding
Start with Recognition
Learn to hear the difference between major and minor chords - the interval changes create distinctly different emotional colors.
Practice Transposition
Take a simple song in one key and move it to another using moveable chord shapes. The structure stays the same, only the starting pitches change.
Connect Theory to Practice
When learning new chords, identify the root note and chord type. Understanding why a chord sounds the way it does helps memorization and musical development.
Open Chord Library
Ready to see these chord structures in action? Check out the Open Chord Library to visualize chord diagrams and see the interval patterns we've discussed.
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What is a Key?
A musical key is a set of notes and chords that work together, centered around a "home" note (the tonic). Keys help organize music and make chord progressions sound natural. Understanding keys is essential for transposing songs, improvising, and writing music.
Explore Chords in Every Key