Originally Posted by: mbgold78
Why does D major scale have 2 sharps? How come the notes don't follow always to the major note like the C major scale does?
I expected
D to E whole step
E to F half step
F to G whole step
G to A Whole step
A to B whole step
B to C half step
C to D whole step
And therefore the shape of the scale is different then the C major scale?
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Because the entire point of the major scale is that it has a specific interval formula creating a unique, individual sound. That interval formula is:

Root (whole step) 2nd (whole step) major 3rd (half step) 4th (whole step) 5th (whole step) major 6th (whole step) major 7th (half step) root

That interval formula is the major scale. If you don't have that set of intervals in that order, you don't have a major scale.

So, we apply that formula across the board. If you want to play a D major scale, you start at the note D & apply the formula & get:

D (whole step) E (whole step) F# (half step) G (whole step) A (whole step) B (whole step) C# (half step) D

D - root
E - 2nd
F# - major 3rd
G - 4th
A - 5th
B - major 6th
C# - major 7th

Contrast that with the sound of the intervals you created.

D - root
E - 2nd
F - minor 3rd
G - 4th
A - 5th
B - major 6th
C - minor 7th

This is D dorian, which is the 2nd mode of the C major scale. Which makes perfect sense, since it's the notes of the C major scale simply starting on the 2nd scale degree. :)
[QUOTE=mbgold78]but Im not getting the point of preserving the shape over preserving the major step.

Also does this shape apply to all major note shapes?

Because the shape preserves the sound of the major scale in the form of the interval formula. Yes, it applies to all major scales. The whole reason each major scale has a different system of sharps or flats is the result of giving each musical alphabet letter the chance to start that unique interval formula.

This tutorial on the circle of fifths covers this issue in depth.

https://www.guitartricks.com/tutorial.php?input=835

Hope this helps! Please ask more if necessary & have fun!