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  • rbedwell3

The Rule of Seven: part one

In music theory, seven is a truly miraculous number. Seven notes in the circle of fifths before the first letter is repeated (hence seven notes scales), seven primary keys. But the use of the number seven I want to discuss today is in key signatures.

Now, I didn't know this until I figured it out a couple of years ago, and I have never read it anywhere else, but when the scales that start on the same letter, say C and C# for instance, have the accidentals added together they always total seven. So what you may ask?

Well, firstly it means that keys are easy to identify, especially for students. 5 flats? Opposite of 2 sharps. 2 sharps = D Major therefore 5 flats = Db Major. Or say 6 sharps? Opposite of 1 flat. 1 flat = F Major therefore 6 sharps = F# Major.

Some of you may then ask, what about G# Major? That contains the notes: G# A# B# C# D# E# F##. That adds up to 8? But G# Major isn't used as a key, Ab Major is. Ab Major is Ab Bb C Db Eb F G. 4 flats. Opposite with 3 sharps? A Major.

Of course, it is the same with minor keys. D Major = B minor = 2 sharps. Db Major = Bb minor = 5 flats.

This is highlighted in the table below. The rule of seven is explained fully in Appendix 3 of my book The Modal Method of Music found here:

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