Starting from each note, every other letter:

Start	Sequence
A	A — C — E — G — B — D — F — A
B	B — D — F — A — C — E — G — B
C	C — E — G — B — D — F — A — C
D	D — F — A — C — E — G — B — D
E	E — G — B — D — F — A — C — E
F	F — A — C — E — G — B — D — F
G	G — B — D — F — A — C — E — G

Any three consecutive notes in a thirds sequence form a triad.

Third	Quality	Half steps
C — E	Major	4
D — F	Minor	3
E — G	Minor	3
F — A	Major	4
G — B	Major	4
A — C	Minor	3
B — D	Minor	3

Three major, four minor.

Use the natural pair as your reference:

• Sharp the bottom or flat the top — shrinks the interval by one half step
• Flat the bottom or sharp the top — stretches the interval by one half step

Modified third	Natural reference	Result
C# — E	C — E (Major)	Minor
F# — A	F — A (Major)	Minor
G# — B	G — B (Major)	Minor
Eb — G	E — G (Minor)	Major
Ab — C	A — C (Minor)	Major
Bb — D	B — D (Minor)	Major
Db — F	D — F (Minor)	Major
D — F#	D — F (Minor)	Major
E — G#	E — G (Minor)	Major
A — C#	A — C (Minor)	Major
B — D#	B — D (Minor)	Major
C — Eb	C — E (Major)	Minor
F — Ab	F — A (Major)	Minor
G — Bb	G — B (Major)	Minor

Start	Sequence
A	A — E — B — F — C — G — D — A
B	B — F — C — G — D — A — E — B
C	C — G — D — A — E — B — F — C
D	D — A — E — B — F — C — G — D
E	E — B — F — C — G — D — A — E
F	F — C — G — D — A — E — B — F
G	G — D — A — E — B — F — C — G

The outer two notes of any triad are a fifth apart.

Fifth	Quality	Half steps
C — G	Perfect	7
D — A	Perfect	7
E — B	Perfect	7
F — C	Perfect	7
G — D	Perfect	7
A — E	Perfect	7
B — F	Diminished	6

Six perfect, one diminished. B — F is the tritone.

The fifths sequence, looping around:

Clockwise (fifths, adds sharps): F — C — G — D — A — E — B

Counter-clockwise (fourths, adds flats): F — Bb — Eb — Ab — Db — Gb

B — F is the seam where sharp keys meet flat keys.

Relative keys are one third apart:

• Relative minor — drop one third from the major key
• Relative major — go up one third from the minor key

Major	Relative minor
C	A minor
Db	Bb minor
D	B minor
Eb	C minor
E	C# minor
F	D minor
F# / Gb	D# / Eb minor
G	E minor
Ab	F minor
A	F# minor
Bb	G minor
B	G# minor