Quote:
Originally Posted by
Its Brady
I've been reading gs for awhile now and I finally decided to post something. Wanted to say thanks for all your guys help. Here's the question I have.
I understand that you can form 7 different chords from each key. Like audio already posted, these are the seven chords for the key of C.
I = C = C E G
ii = Dm = D F A
iii = Em = E G B
IV = F = F A C
V = G = G B D
vi = Am = A C E
vii-dim = Bm dim = B D F
But how do you know that these are the 7 chords? What type of formula does this follow?
Thanks
You create the respective triads by stacking consecutive thirds upon each other, 4 note chords are a bit different though.
They follow the church modes of old named after the greek islands. You form every diatonic chord in the scale by pressing every other note in the scale. This changes a tad for some chords when you hit dominant 7, major 7, minor 7 etc or any other higher permutation of chords, 9ths 11ths 13ths flat 9s etc.
But for your standard diatonic triads, stack a consecutive third on each note and in regards to diatonic 7 chords, they are formed off your church modes, Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian and Locrian. Hit every other note in the scale and it will form its respective diatonic chord.
Diatonic I chord - C - skip D - E - skip F - G
Diatonic II chord - D - skip E - F skip G - A
etc etc etc
These carry on and form your basic
I IV, V diatonic major chords
II III,VI minor chords
and your diminished 7 chord For major scales.
For minor scales it is the same however in western music the harmonic minor is used in which you sharp the 7th degree of the scale to create increased tension between the leading tone and the tonic. So if you were in C minor (C D Eb F G Ab Bb) the Bb would become B and in turn the 5 chord would be a major chord instead of a minor resulting from this raising. Turning what would normally be G minor chord into a G major chord.
Try it: Play 2 I IV V chord progressions
1. Using the natural minor C Eb G - F Ab C - G Bb D
2. Using the harmonic minor C Eb G - F Ab C - G B D
you will see how the second progression sounds much more tense, like it is waiting for something.
The above does not hold true for the minor 7th chord tonic 1 chord. The the C minor 7 chord would thus still be C Eb G Bb and not C Eb G B.
This in turn gives you the formula
Tonic I and Subdominant IV minor chords
Mediant III, Dominant V and Submediant VI Major chords
and Supertonic II and Leading tone VII diminished chords.
The diatonic III chord in minor scales is sometimes augmented in keeping with the harmonic variant of major scales.
Again remember though this changes sometimes when you hit 4 note chords of certain chords. For example it is commonly accepted that the V7 is a dominant 7 chord, however in a 1 4 5 progression if the major 7 chord ( G B D F#, notice F# is a non diatonic note) sounds better to you then by all means use it, not to say that it is wrong to use it but a large part of this comes down to artistic preference, bending the rules without breaking them. Which is why someone in their previous post put "allowed" in quotations.