Chords/scales and Roman Numerals

As I sit here, finally enjoying.....breakfast, my mind is full of music theory that I want to share with you.
So here we go!

In the last post we looked at three different major chords (C, F, G) and making them into dominant 7th (or 7th) chords. Now that we have three major chords of a major scale (C major scale) we can look at how Roman numerals interact with chords and scales.

Roman numerals follow the same pattern as scale degrees (1, 2, 3, 4, 5, etc). It just looks different:
I, ii, iii, IV, V, vi, vii, VIII (usually written as I). There is a reason we are using upper case and lower case Roman numerals and it's very simple. The upper case tells us which chords are major and the lower case tell us which chords are minor. It looks like this:                                                                
                                                                                                                                                                 
C         D         E         F         G         A         B         C                                                                          
I          ii          iii        IV        V        vi         vii         I                                                                            
1         2           3         4          5         6          7          1    (scale degrees)                                                

Now, I know we haven't gotten into how minor scales/chords are created, so we will look at that now.

Changing scales and chords from major to minor or diminished is really just a formula that you need to memorize. The first step in that formula has already been done when we changed the major 7th chord to a dominant 7th chord by flatting (lowering the 7th a half step) the 7th (B to Bb). The second step in the formula creates the minor scale/chord:                                                  

C minor scale - C        D        Eb        F        G        A        Bb        C                                                    
                         1         2         3          4         5         6         7           8 (or I)                                          

So the formula to change a major to a minor goes like this:                                                                  
1. flat the 7th  (Bb in C scale)                                                                                                    
2. flat the 3rd (Eb in C scale)                                                                                                                
Now you have C minor scale. To make the C minor 7th  chord you just use the 1, 3b, 5, 7b =            
C, Eb, G, Bb

So there is the first two steps in the formula that helps change chords. The next two steps will show us how to write/play diminished chords. There are two types of diminished chords. The first is a half diminished (symbol = usually a C with a circle-o with a slash through it). This is the third step in the formula:
C, Eb, Gb, Bb  OR  1, 3b, 5b, 7b = either way, you have flatted the 5th (lowered it a half step) and  your half diminished chord.
The formula to create a half diminished chord is this (using the C scale):
1. flat the 7th (Bb)
2. flat the 3rd (Eb)
3. flat the 5th (Gb)

The next step will make it a full diminished chord. You flat the 7th AGAIN. This is called double flatting or lowering the note (7th) two half steps:                                                                                  
C, Eb, Gb, Bbb   OR   1, 3b, 5b, 7bb = either way - full diminished chord.
The formula (C scale):
1. flat the 7th (Bb)
2. flat the 3rd (Eb)
3. flat the 5th (Gb)
4. flat the 7th AGAIN (Bbb)


Any confusion or questions? Let me know and thanks for reading.