Major Scales

The major scale is the foundation of Western tonal music. Every key, every key signature, every diatonic chord progression starts here. If you know your major scales in all twelve keys, you have the framework that everything else hangs on — modes, chord tones, extensions, and voice leading all derive from knowing where the notes are and how they relate.

Construction

A major scale is seven notes built from a specific pattern of whole steps (W) and half steps (H):

W — W — H — W — W — W — H
1   2   3   4   5   6   7   (8=1, octave)

Half steps occur between scale degrees 3-4 and 7-8 (7-1).

The pattern works from any starting note. C major produces no sharps or flats. Every other root requires sharps or flats to maintain the W-W-H-W-W-W-H spacing.

All Twelve Major Scales

Key	Notes	Sharps/Flats
C major	C D E F G A B	None
G major	G A B C D E F#	1# (F#)
D major	D E F# G A B C#	2# (F#, C#)
A major	A B C# D E F# G#	3# (F#, C#, G#)
E major	E F# G# A B C# D#	4# (F#, C#, G#, D#)
B major	B C# D# E F# G# A#	5# (F#, C#, G#, D#, A#)
F# major	F# G# A# B C# D# E#	6# (+ E#)
C# major	C# D# E# F# G# A# B#	7# (all)
F major	F G A B♭ C D E	1♭ (B♭)
B♭ major	B♭ C D E♭ F G A	2♭ (B♭, E♭)
E♭ major	E♭ F G A♭ B♭ C D	3♭ (B♭, E♭, A♭)
A♭ major	A♭ B♭ C D♭ E♭ F G	4♭ (+ D♭)
D♭ major	D♭ E♭ F G♭ A♭ B♭ C	5♭ (+ G♭)
G♭ major	G♭ A♭ B♭ C♭ D♭ E♭ F	6♭ (+ C♭)

Key Signature Rules

Order of sharps: F C G D A E B   (each new sharp key adds one more)
Order of flats:  B E A D G C F   (reverse of sharps)

Sharps: the key is one half step above the last sharp.
  G major: 1# (F#) → key is one half step above F# = G ✓

Flats: the key is the second-to-last flat.
  B♭ major: 2♭ (B♭, E♭) → second-to-last flat = B♭ ✓
  (C major is the special case: no flats, no sharps)

The Diatonic Chords

Build a triad or seventh chord on each scale degree using only notes of the key. The chord quality pattern is the same in every major key:

Degree	Numeral	Quality	In C major	Function
1st	I	Major 7th	Cmaj7	Tonic — home, resolved
2nd	ii	Minor 7th	Dm7	Subdominant — movement away from tonic
3rd	iii	Minor 7th	Em7	Often substitutes for tonic
4th	IV	Major 7th	Fmaj7	Subdominant — strong contrast
5th	V	Dominant 7th	G7	Dominant — strongest pull to tonic
6th	vi	Minor 7th	Am7	Relative minor — tonic-like quality
7th	vii°	Half-diminished (m7♭5)	Bm7♭5	Dominant function, leading tone chord

Circle of Fifths

Moving clockwise: add one sharp each step
Moving counter-clockwise: add one flat each step

    C (0)
F(1♭)     G(1#)
B♭(2♭)   D(2#)
E♭(3♭)   A(3#)
A♭(4♭)   E(4#)
D♭(5♭)   B(5#)
    G♭/F#(6♭/6#)

Adjacent keys (one step apart) are closely related — modulations between them
sound natural because they share six of seven notes.

Relative and Parallel Relationships

Relative minor: built on the 6th degree of the major scale.
  C major → A natural minor (same notes, different tonal centre)
  G major → E natural minor
  
Parallel minor: same root, different key signature.
  C major (C D E F G A B) → C minor (C D E♭ F G A♭ B♭)
  Parallel keys produce modal interchange — borrowing chords across the parallel.

The major 7th chord (I) is the most stable, at rest.
The dominant 7th (V) is the most active, pulling back to I.
This tension and resolution is the engine of tonal music.

Intervals Within the Major Scale

Scale degree	Interval from root	Semitones	Example (C)
2nd	Major 2nd	2	D
3rd	Major 3rd	4	E
4th	Perfect 4th	5	F
5th	Perfect 5th	7	G
6th	Major 6th	9	A
7th	Major 7th	11	B
Octave	Perfect octave	12	C

References

Levine — The Jazz Theory Book
Aldwell & Schachter — Harmony and Voice Leading
musictheory.net — Key Signatures ↗