The notes of the C major scale are
C D E F G A B
1 2 3 4 5 6 7
The C major chord comprises of the 1st, 3rd and the 5th note of the C scale i.e C E G. Once you know the notes that make up the major chord deriving any other chord is a piece of cake.
I always wondered what the minor chord was. But if you look closely it's just the major chord with the 2nd note of the chord flattened by a semitone. So when to flatten the 2nd note of the C major chord from E to Eb, you get C Eb G which is the C minor chord
A semitone is the smallest musical interval used in Western music.It is the distance between two notes which are next to one another in pitch.
In order to find out the augmented chord you have to know the major chord. Then just sharpen the 3rd note of the major chord by a semitone. So to get the Caug chord, from the C major chord, i.e. C E G, sharpen the G note to G#. This gives you the C augmented chord - C E G#.
A diminished chord can be derived from its minor chord. When the 3rd note of a minor chord is flattened by a semitone you get a diminished chord. Thus for a C dim chord, when the G note of a Cmin chord is flattened to Gb, you get C Eb and Gb which is the C dim chord
In order to get the 7th chord, after finding the corresponding major chord, add the flattened 7th note of the scale to the major chord and bingo... you get the 7th chord. In case of C scale the 7th note is B and flattened 7th is Bb. So if you add Bb to C major chord, you get C E G Bb which is the C7 chord.
When you take the 1st, 4th and 5th note of the scale you get a suspended fourth chord. Thus the Csus4 chord comprises of the notes C F G.
In order to get the ninth chord, you have to add the 9th note of the major scale to the seventh chord. But how do you get the ninth note of a scale? Let’s look at the C major scale. The C note is the 1st note, then D is the 2nd note and so on. When you reach B, that’s the 7th note and then back to C. Now the C after the B note is considered the 8th note, and then the D note is the 9th note
C D E F G A B C D E …
1 2 3 4 5 6 7 8 9 10
Add D note to the C7 chord and this gives you the C9 chord which is C E G Bb D. Easy isn't it?
Hope this article helped demystify chords. If you have any comments or suggestions let me know and I will get back to you.