Building Chords- Using Scales to Make Major, Minor, and Sus2 and Sus4 chords

See the section on major scale.

A basic chord is built on 3 notes. These 3 note chords are called “triads”. Other notes can be added to a tried to make “extensions”. This lesson will focus just on triads.
There are 6 important types of chords that you need to know: Major chords, minor chords, diminished chords, augmented chords, sus chords, and 5 chords. Major and Minor chords are the most important chords in western music. Diminished chords are also very important. Major chords are said to have a “happy” tone while minor chords are said to have a “sad” tone. Diminished chords are great for building tension. This lesson will explain how to make major, minor, and diminished chords. So lets build some chords.
If you remember from the lesson on the major scale, there are 7 notes in the major scale. By taking certain notes out of this scale we can build a triad. So what notes do we take? Well that depends on what chord we want to build.
Lets name the notes in the scale from 1 to 8(Last note is same as 1st note)....For eg. consider C scale:

The Formula’s for major and minor chords are as follows:
Major: 1-3-5 . So that means you take the 1st, the 3rd note and the 5th note and play them together. That gives you a major triad. In case of C chord we have CEG notes covered.
Minor: 1-3b-5. Minor chords are made by taking the 1st note, the b3rd (this means you “flat” the 3rd note by moving it down one half-step), and the 5th note. In case of Cmin, we have D# instead of E in CEG...So minor chord of C changes to CD#G or CEbG.
Diminished: 1-3b-5b. Diminished chords are made by playing the 1st note and flatting both the 3rd and the 5th notes of a scale. In case of Cdim chord is CEbGb or CD#A#.
So the difference between a major and minor triad is the 3rd note. A minor triad has a flat third note.
You will notice that to build a chord we are stacking either Major 3rd or minor 3rd intervals on top of each other. So chords are made by stacking 3rds. (If you don't know what I'm talking about see my post on intervals).

So if we want to make a C minor chord all we have to do is flat the 3rd. So lets move the E note down one half step. So C minor would be C, Eb, G. Got it? And what would a C diminished chord be?
You got it. C, Eb, Gb. (because we flat the 3rd and 5th notes!)
Now lets look at the guitar chord charts and see how to play these chords.

Some more examples.

Understanding Tone difference in Tone