Originally Posted By: GHinCH
Originally Posted By: Noel96
The key signatures that have flat and sharp equivalents are Cb/B, Gb/F#, Db/C#.


This one I don't understand.

(I always thought that G#/Ab, A#/Bb, and D#/Eb are also equivalent, as well as E#/F, E/Fb, B#/C and in Germanic notation: Hb/B; B#/H smile (the last two don't make sense in English: Bb/Bb, Bb#/B))


Hi,

What I was meaning was key signatures and not single notes.

For example....

a) Key sig of Cb major (7 flats) = Cb Db Eb Fb Gb Ab Bb Cb
b) Key sig of B major (5 sharps) = B C# D# E F# G# A# B

These two scales have exactly the same notes. The only difference is that one is written using sharps and one is written using flats. This same principle holds true for the other two key signatures I mentioned (Db/C#, Gb/F#).


The reason that the remaining key signatures are unique is because to notate them as enharmonic equivalents, one needs to use double sharps and double flats.

For example, consider using the notes Ab and G# as the basis for major scales. To do so requires the following....

c) Key sig of Ab major (4 flats) = Ab Bb C Db Eb F G Ab
d) Key sig of G# major (6 sharps, 1 double sharp) = G# A# B# C# D# E# F## G#

I constructed the above using the major scale neighbouring note relationship of "root note, tone, tone, semitone, tone, tone, tone, semitone, root note" in addition to the fact that each note of the scale must be part of an alphabetical sequence.

The music notation system of western music doesn't accommodate double sharps or double flats in the key signature position. This means it's not possible to notate the key signature of G# major.

Hope this helps to explain what I mean.

Regards,
Noel

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