Major Scale
We have been looking at this scale a lot. It was one of the Medieval modes. From Renaissance times on it became a predominant scale in Western music, and is one of only two scale types that we use in conventional music. This scale is called the major scale. The other type of scale we still use is the minor scale.
Now, rather than playing a mode on D, (d e f g a b c d) we now recreate the sound of the major scale starting on D. This means we have to adjust some of the notes. This is what the D major scale looks like. Instead of playin F we have to play F#, and instead of C, C#. We do this to maintain the sound and feel of a major scale. Listen to the video to compare C Major, D Major and D mode.
More about the Major scale.
Six String Theory