Originally Posted by Rutherford_Fan
Next, harmonize the scale. That is, using only scale tones, stack thirds on each note as its own root. So for C, you will get CEbG, a C Minor chord. For Eb, you will get EbGBb, which interval-wise, is a Eb Major Chord.
- and brings us to stacking 3rds to get the chords to use with that, or any, scale.
Go stack some scales if you have not done so already, guarantee it will open all kinds of doors. Was a hugh WOW for me the first time I did it. Here is the C major scale stacked. Use it as a Rosetta stone for stacking the C natural minor scale (Aeolina) listed above.
C Major Scale stack in 3rds (every other note) = the notes and chords made from the C major scale:
Notes Degree Spelling Chord name Function
C R CEGB R-3-5-7 Cmaj7 I (tonic)
D 2 DFAC R-b3-5-b7 Dm7 ii
E 3 EGBD R-b3-5-b7 Em7 iii
F 4 FACE R-3-5-7 Fmaj7 IV (subdominant)
G 5 GBDF R-3-5-b7 G7 V (dominant)
A 6 ACEG R-b3-5-b7 Am7 vi
B 7 BDFA R-b3-b5-b7 Bm7b5 vii (diminished)
Notice we have taken this stack out to the 7th note.
Why is the D chord minor? If you compare the DFAC to the notes in the D major scale the D major scale will have an F# and a C#. Your DFAC has the 3 and 7 flatted for a spelling of R-b3-5-b7 and that spelling makes a Dm7 chord. All minor chords will have a b3. All major chords will have a natural 3. Stacking the scale in 3rds automatically build the correct major, minor and diminished chords for that scale.
Might come in handy. http://www.smithfowler.org/music/Chord_Formulas.htm