How to make a diatonic scale

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Pick a letter from A to G, accidental natural, sharp or flat. Follow through with the natural letters of the alphabet.

A B C D E F G A
 T S T T S T T 

The pattern of tones and semitones from A to A is TSTTSTT. This is not TTSTTTS. It is not a diatonic scale.

We use accidentals to make a diatonic scale.

  1. The first interval of the diatonic scale is T.
    • Start with the first note (A).
    • A to B is T.
    • B is the second note of the diatonic scale.
  2. The second interval of the diatonic scale is T.
    • Start with the second note (B).
    • B to C is S.
    • B to C# is T.
    • The third note of the diatonic scale is C#.
  3. The third interval of the diatonic scale is S.
    • Start with the third note (C#).
    • C# to D is S.
    • The fourth note is D.
  4. The fourth interval of the diatonic scale is T.
    • Start with the fourth note (D).
    • D to E is T.
    • The fifth note is E.
  5. The fifth interval of the diatonic scale is T.
    • Start with the fifth note (E).
    • E to F is S.
    • E to F# is T.
    • The sixth note is F#.
  6. The sixth interval of the diatonic scale is T.
    • Start with the sixth note (F#).
    • F# to G is S.
    • F# to G# is T.
    • The seventh note is G#.
  7. The seventh interval of the diatonic scale is S.
    • Start with the seventh note (G#).
    • G# to A is S.
    • The eighth note is A, the same as the first.

The diatonic scale of A is:

A B C# D E F# G# A
 T T S T T T S 

How to work magic

Can a diatonic scale be written to D# ?

No.

D#
Eb		E
Fb		F
E#		F#
Gb		GG#
Ab		AA#
Bb		B
Cb		C
B#		C#
Db		DD#
Eb
D# E#  GG# A# B#X DD#

Why not?

What is wrong with D# E# G G# A# B# D D#.

Answer: C is missing and G is repeated.

Every letter must be present in a diatonic scale.

What can we do?

We can introduce double sharps and double flats. Fx is G and Cx is D.

This is also wrong D# E# Fx G# A# B# Cx D#

Double sharps and double flats are banned from diatonic scales.

What can we do?

Rename each note to its enharmonic.

Now we have a diatonic scale.

Eb F G AB Bb C D Eb

Every key on the keyboard can be written to a diatonic scale, but not every note name. When the first name you try doesn’t work, switch to its enharmonic. It’s enharmonic will work.

 C#
dB		 D#
Eb		  F#
GB		 G#
AB		 A#
Bb		 
C
B#		DE
Fb		F
E#		GAB
CB