What is a chord? A chord is a group of notes (generally 3 or more) which when played together make up a basis of harmony.
Chords are made up of notes that belong to scales. Each chord has a corresponding scale.
If you are not sure what a scale is, then read my blog about C Major Scale for guitar here.
There are 3 basic categories or types of chords that you should learn.
Triads are 3 note chords. They can be major, minor, diminished, augmented, or suspended chords. Although triads are exactly 3 notes, you can play major, minor, diminished, augmented and suspended chords with more notes by simply doubling some of the notes. All the CAGED chord forms that most beginners learn use double notes.
These are 4 note chords that have a seventh degree, which is a note that is usually a major or minor seventh interval above the root. The most common seventh chords are major 7, minor 7, and dominant 7.
Extended chords are simply chords that contain a ninth, eleventh, or thirteenth. These are considered the extended notes. You should notice that they could also be considered the 2, 4, or 6. For example, in the key of C, the 2nd and 9th are both D. The 4th and 11th are both F. The 6th and 13th are both A.
If it sounds complicated, don't worry and don't give up. It's best to take it slow and we'll only be covering basic triads for major chords here.
Music Theory for Guitarists: learn and understand chord construction.
scale formula + major scale
If you know the major scale, this is an easy approach.
You choose a root note, such as C
You get its major scale notes: C-D-E-F-G-A-B.
You apply a chord formula for major scale
For example, the chord formula for major chords is 1-3-5. We take the first, third, and fifth note of the major scale to create this chord.
C Major Scale:
C . D . E . F . G . A . B . C .
1 . 2 . 3 . 4 5 . 6 . 7 . 1
C Major chord has the notes C-E-G.
It is important to note that chords can have the same notes twice.. For example, C Major in open position doubles a C (2nd and 5th string) and an E (1st and 4th string)
List of Triad formulas for Chords