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Music Theory Visual Guide

Understand the fundamentals that underpin all of Western music — from key signatures to chord progressions.

Circle of Fifths

The universal map of musical keys. Click any key to see its diatonic chords and key signature.

CGDAEB/CbF#/GbDb/C#AbEbBbFAmEmBmF#mC#mG#mEbmBbmFmCmGmDmCircleof Fifths

Key Signatures Reference

KeySharps/FlatsNotesRelative Minor
C majorNoneC D E F G A BA minor
G major1♯ (F#)G A B C D E F#E minor
D major2♯ (F#, C#)D E F# G A B C#B minor
A major3♯ (F#, C#, G#)A B C# D E F# G#F# minor
E major4♯E F# G# A B C# D#C# minor
F major1♭ (Bb)F G A Bb C D ED minor
Bb major2♭ (Bb, Eb)Bb C D Eb F G AG minor
Eb major3♭Eb F G Ab Bb C DC minor
Ab major4♭Ab Bb C Db Eb F GF minor

The 7 Musical Modes

Ionian (Major)

"Bright, Happy"

1 2 3 4 5 6 7
e.g. C D E F G A B

Dorian

"Minor + jazzy brightness"

1 2 ♭3 4 5 6 ♭7
e.g. D E F G A B C

Phrygian

"Dark, Spanish"

1 ♭2 ♭3 4 5 ♭6 ♭7
e.g. E F G A B C D

Lydian

"Dreamy, ethereal"

1 2 3 ♯4 5 6 7
e.g. F G A B C D E

Mixolydian

"Major + bluesy"

1 2 3 4 5 6 ♭7
e.g. G A B C D E F

Aeolian (Natural Minor)

"Sad, Melancholic"

1 2 ♭3 4 5 ♭6 ♭7
e.g. A B C D E F G

Locrian

"Unstable, Dissonant"

1 ♭2 ♭3 4 ♭5 ♭6 ♭7
e.g. B C D E F G A
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Music Theory: The Foundation of All Western Music

Music theory might sound intimidating, but at its core it's simply the grammar of music — the rules and patterns that explain why certain combinations of notes and chords sound the way they do. Whether you want to write original songs, improvise confidently, or simply understand what's happening in your favorite music, a grasp of theory fundamentals will transform your musicianship.

Why Learn the Circle of Fifths?

The circle of fifths is the single most useful diagram in Western music theory. It organizes all 12 major and 12 minor keys into a circular pattern where adjacent keys share the most notes in common (six out of seven). This relationship explains why modulating (moving) between neighboring keys sounds smooth and natural, while jumping across the circle creates dramatic contrast.

Practically, the circle of fifths helps you instantly know: how many sharps or flats a key uses, which minor key has the same key signature as any given major key, which chords are most likely to work together, and how to plan key changes in your own compositions.

Diatonic Harmony: Building Chords from a Scale

When you stack thirds on each note of a major scale, you get the seven diatonic chords that naturally belong to that key. In C major: C major (I), D minor (ii), E minor (iii), F major (IV), G major (V), A minor (vi), and B diminished (vii°). Understanding which chords naturally belong together is the first step toward being able to play by ear and improvise.

FAQ

Music Theory — Frequently Asked Questions

What is the circle of fifths used for?
The circle of fifths is a fundamental music theory diagram that shows the relationship between all 12 major and minor keys. Musicians use it to understand key signatures, find related keys for modulation, figure out which chords naturally belong to a key, and understand why certain chord progressions sound harmonically pleasing.
How many sharps or flats does each key have?
Keys are arranged in the circle so that each step clockwise adds one sharp, and each step counterclockwise adds one flat. C major has no sharps or flats, G major has 1 sharp, D major has 2 sharps, while F major has 1 flat, Bb major has 2 flats, and so on up to 7 sharps (C# major) or 7 flats (Cb major).
What is a relative minor key?
Every major key has a relative minor key that shares the same key signature (same notes and sharps/flats). The relative minor starts 3 semitones below the major key. For example, A minor is the relative minor of C major — both use no sharps or flats.
What are the diatonic chords of a key?
Diatonic chords are the 7 chords that naturally occur within a key using only that key's notes. In C major, they are C, Dm, Em, F, G, Am, and Bdim. These chords all sound naturally harmonious when played together.
What does a key signature tell you?
A key signature tells you which notes are consistently sharp or flat throughout a piece. It appears at the beginning of sheet music after the clef. It saves you from writing a sharp or flat symbol before every affected note.
What is a musical mode?
Modes are scales derived from the major scale by starting on different degrees. The seven modes are Ionian (major), Dorian, Phrygian, Lydian, Mixolydian, Aeolian (natural minor), and Locrian. Each mode has a unique sound character — Dorian sounds jazzy, Phrygian sounds Spanish, Lydian sounds dreamy.
What is the difference between major and minor keys?
Major keys have an interval pattern with a major third (4 semitones) from the root, giving them a bright, happy sound. Minor keys have a minor third (3 semitones), giving them a darker, sadder feel. The natural minor scale is also called the Aeolian mode.
What is a chord progression?
A chord progression is a sequence of chords played in order. Common progressions include I–V–vi–IV (found in countless pop songs), ii–V–I (common in jazz), and I–IV–V (the foundation of blues and rock). Roman numerals indicate each chord's position within the key.
How do I transpose a song to a different key?
To transpose, shift every chord by the same number of semitones. If you want to move from C major up to D major (2 semitones up), C becomes D, F becomes G, G becomes A, and Am becomes Bm. Our Transpose Tool on the tools page automates this process for you.
What is a tritone and why is it important?
The tritone (augmented fourth / diminished fifth) spans exactly 6 semitones and is the most harmonically tense interval. It's the interval between the 4th and 7th degrees of a dominant 7th chord (like G7: G–B–D–F, where B to F is a tritone). This tension drives the V7→I resolution that creates satisfying harmonic movement.