D Major Scale = D-E-F#-G-A-B-C#
D# Major Scale = D#-E#-F##-G#-A#-B#-C##
What happened? Each note was only moved up one half step and what a mess it made. Let's convert the E#, etc.......... to see what happens.
D#-F-G-G#-A#-C-D
in Tonally it sounds fine, but in note value it couldn't be read, written, measured or communicated properly without utter confusion.
There's no E or B measure, but has 2 G's & 2 D's to trip over.
Music is created from time, so is a Clock. It's not ever 3:05pm and just skip to 3:15pm, without first having a 3:10 pm measure.
The half step interval between D and E must work somehow. Try one half step down from E to Eb. It fits in the slot and it's notes are one half step lower than the E Major scale
E Major Scale = E-F#-G#-A-B-C#-D#
Eb Major scale = Eb-F-G-Ab-Bb-C-D
It's a perfect fit and all notes are in order.
One important clue common in all Major Keys are that All of the Keys that use sharpened notes for proper order have a Natural as the Tonic, except one, F# Major, which is the last Key to use sharps and contains the most sharpened notes. 6 of 7 notes are # in the Key of F# Major.
Those that Flatten, all have flattened notes as the Tonic, except one, F Major, which is the first note to use flats and contains only one flat note in Key.
Gb Major contains 6 flats (F# Major contains 6 sharps).
How can a 7 note Diatonic Scale contain 6 accidentals when there are only 12 semitones from Unison to the Octive and 7 of the 12 tones are Natural notes? A BC D EF G A-- This is just an order of letters given a title to identify different tonal function. The Interval placement is what connects the letter to each note so that composition can exist through written form and be translated into tonal harmony so it can be heard through precise interpretation by the composer's true expression.
With 7 Natural tones, that leaves only 5 semitone intervals for accidentals; 7+5=12.. The 5 fall Between A(1)B, C(2)D, D(3)E, F(4)G, G(5)A.
Since intervals govern the notes in precise order, each note needs to have a clear and exact distinction to be transcribed without conflicting with another note sharing the title. (G-G#)
Intervals set the order and title of notes. There won't be a C# and a Eb mixed within the same key signature. #'s with #'s and b's with b's.There will be an instance where Cb or E# is used to keep proper order in a key. Example;
Gb Major = Gb-Ab-Bb-Cb-Db-Eb-F
F# Major = F#-G#-A#-B-C#-D#-E#
With E#= F, Placing the F in the Key complicates writing and reading music in clarity by having 2 F's in a key signature. Placing the # key signature just after the Clef is clear that notes play sharp without the need to mark each one and reduces a clutter. To play the F, a natural notation would be needed to cancel playing #'s. E# flows and keeps order following the D#.
