Circle of Fifths

[pinkfloyd87]

Minors: I ii iii IV V vi (vii Diminished)
Lowercase means minor, upper is major.

Key of C – No sharps or flats
Model: C D E F G A B C

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So if you wanted to play in the key of G, you’d lower the G half a step and that would be your sharp (F# in this case), thus having:
G A B C D E F# G
Now with the minors added: G Am Bm C D Em F#dim G

Going down the circle clockwise, we come to D. The fifth of G is D, and that’s why it comes next. Coming down half a step from D is C#, which is your new sharp. The D model looks like this:
D E F# G A B C# D
Minors added: D Em F#m G A Bm C#dim D

The fifth of D is A. Dropping down a half step from A is G#. Model:
A Bm C#m D E F#m G#dim A

The fifth of A is E. Dropping down another half step is D#. So the E model is:
E F#m G#m A B C#m D#dim E

The fifth of E is B. Coming down a half step from B is A#. Model:
B C#m D#m E F# G#m A#dim B

So on and so forth.